DOCUMENT RFSUME

ED 025 119 EF 002 314

Heating. Ventilation, Air Conditioning Resource Manual for Custodial Training Course #3.Florida State Dept. of Education, Tallahassee. School Plant Management Section.Pub Date Sep 65Note- 143p.EDRS Price MF-$0.75 HC-$7.25Descriptors-*Air Conditioning amate Control, *Custodian Training, Equipment Ma,ntenance. Guidelines.*Heating Instructional Matenats, Manuals, Mechanical Equipment. *Resource Guides. School Maintenance.Thermal Environment, *Ventilation

Intended as a manual to provide school custodians with some understanding ofbasic functions of heating, ventilating, and air conditioning equipment for safe.efficient operation. Contains general rules and specifications for providing custodianswith a more complete awareness of their equipment and the field of "Climate Control-within the school. Chapters include--(1) What is Heat? Cold? Energy7, (2) FactorsDetermining Health and Comfort, (3) Heating Systems, (4) Heat Generators. (5) Fuelsand Combustion, (6) Daily Procedures for Heating Devices, (7) Boder Care. (8)Ventilation. (9) Air Conditioning. (10) Control Systems, and (I I) Heat Pumps. A briefhistory of heating and a comprehensive glossary are also included. (RH)

t' 4 4,4 1*,0 R

0

0 010

r--N

tr#14",

64.

S.

oramenalwal

..,.._________...._....4 ' ts ..0.4.*t --...0 4-, ,..x._ -i "

..;i1',.. 4 ,rt..."4/'ki? '41, 7,n4.1,40 -tir.,........, , et .

N.r',1,-....ti,.,... ..1-4. :".... ',.....,7

4'sibe.'"i"0 .4-f:2*4 A r:11,12444V,:'

lIk'a,, Act Azzve...,t.-..tb, . 44.44 ....3. ,, ?, ,.. »it ,..- 4,7,0,, t-t's: " .m...., ^- " ,v9-2e.,-. ..

tn.1.-.1- ':P.1`. , S.-=;4-:',11Li,,-40.--10.-474!Cli: ..\_:wo...`,.V,ILY:ft...14,1-!e'-ift,,,,.... 4,:k" 0,../.61.4,4.1, .

,,7-34,06,. I.. rw. ,-Ny.._:. ,;;/...-v. .

-4 4` h.' ' - ' ti ..'s . '1%-voanr-t, 4414 1.4144 .1.4.4 ", Sw, ..;(4,- .

k.,.'"..i.x-,,p

-g4,.. .14..r,,,-4.124tr,41,-,-., .44,sz. ziA. -to-

i' s7 -.IS . t%1 ;XX cra,W4, 14 paz 14.,44.4,.. `'''..e., a m, '.. 4- '',7,44tVIV 0414 V4:4'tl°.:1 .41 A '. 14)",14:t54.r1fLAI'.. "t"' ''-oo-r..;,.."

r=1: '" ''-.' " . le.o-1. to .11, -./.;... '- -... A ',..,- ;,...w.- ....._.L...9

'' erf.11.;4\74!?, ''''- .. t'. ..t, e , - 4. ;,..

-, 1 4404.1,i.t I a if Ntd. . ':'$. ,1.'. .......4...^.4 4 c MIN,104, ....7 - .. *. ' .

.41S4=6,.1.. 7.a:111Eiii4141,,,OLF.W.*',.. . a . a e %, ' . i . . ..'

VIV001111**(11101jEliailt:iFieI

..daampoureiaml

*ie z-oc=1.9s

Vf.

Prepared by:

School Plant ManagementState Department of

EducationTallahassee, Florida

U.S. DEPARTMENT Of MM. EDUCATION 8 WELFARE

OFFICE Of EDUCATION

THIS DOCUMENT HAS SEEN REPRODUCED EXACTLY AS RECEIVED IRON THE

PERSON OR ORGANIZATION ORIGINATING IT. POINTS OF VIEW OR OPINIONS

STATED DO ii01 NECESSARILY REPRESENT OFFICIAL OFFICE OF EDUCATION

POSITION OR POLICY.

RESOURCE MANUAL

for

CUSTODIAL TRAINING COURSE #3

HEATINGVENTILATION ED025119

AIR CONDITIONING

Additional copies may be obtained by writing to:

School Plant Management Section:

State Department of Education

Tallahassee, Florida

September, 1965

FOREWORD

Modern concepts of air-conditioning embrace the functions of air

heating, air cooling, humidity control, and air distribution. Distribution

in turn implies the delivery of fresh air and the removal of used air. These

functions in a school environment are important in achieving student and

staff comfort, efficiency and health.

Each school building should be designed so that the atmosphere of the

interior is kept at healthful levels of temperature and humidity, and

drafts are avoided. Proper heating, cooling, and distribution of air are

conducive to pupil and staff comfort and efficiency and are a deterrent to

upper respiratory infections.

The most carefully designed and manufactured air tempering system is

of little value if the person who is to operate it does not understand the

basic functions, and the proper operation and care of ale system. Lack of

knowledge of the proper operation, recognition of danger symptoms, and improper

maintenance can permit situations to develop which can be harmful to the equip-

ment as well as to the occupants.

It is hoped that this course, designed for school custodians will provide

some understanding of the basic functions of heating, ventilating, and cooling

equipment, as well as general rules for safe, efficient operation. With so many

manufacturers, models, and modifications, it would tot be practical to attempt

to cover specific details for each piece of equipment available. The general

rules contained in this manual are intended to give the school custodian a

greater understanding of his equipment and the field of "climate control" within

the school.

ACKNOWLEDGMENTS

The materials in this manual were prepared by Mr. Walter E. Kowall,

Coordinator of Custodial and Maintenance Training, with the assistance and

advice of Mr. Nelson E. Viles, Jr., Consultant, School Plant Management and

Insurance, and Mr. Luther S. Smith, for his original research and format.

Information came from many sources including the literature in the field and

experience gained while working in the school districts.

Appreciation is extended to the many members of the Florida School Plant

Management Association, and to Mr. Paul Stanley, Polk County School System.

Special recognition is given to the following companies for their assistance:

Airtherm Manufacturing Company

American Standard

Calgon Corporation

Hoffman Specialty Manufacturing Corporation

Kritzer Radiant Coils, Inc.

McMillan Comfortaire, Inc.

Minneapolis-Honeywell Regulator Company

Peerless Heater Company

Titusville Iron Works

Weil-McLain Company, Inc.

Particular appreciation is extended to Mr. C. W. Nessell, for permission

to use excerpts from his article on the, "History of Heating". We also ish to

express our appreciation to the University of Nebraska Press for permission to

use material in "Handbook for School Custodians", Fifth Edition, by

Mr. Alanson D. Brainard as revised by Mr. A. E. Goedeken.

iii

TABLE OF CONTENTS

FOREWORD

ACKNOWLEDGMENTS

INTRODUCTION - HISTORY OF HEATING ......... . . . .

CHAPTER

General

What is heat? Cold? Energy? Energy transfer?

Energy equivalents; definitions17

II ractots Determining Health and Comfort

Temperature, humidity, odor control, air movement,

dust, noise, activity, etc33

III Heating Systems

Advantages and disadvantages of six types of systems. 41

IV Heat Generators

Classification of steam systems; Boiler parts and

Oleir uses; Care of the boiler53

V Fuels and Combustion

Gas - natural and manufactured; Fuel oils;

Theory of combustion; Burners; Controls69

VI Daily Procedures for Heating Devices

Pre-start procedures; Blowdown; Locating boiler

trouble; Things to remember when operating a boiler;

Economies in heating85

CHAPTER

VII Boiler Care

Cleaning; Tube and flue care; Flue gas analysis;

Electrolysis; Boiler compounds; Preparing for

summer lay-up - wet or dry method 97

VIII Ventilation

Methods; Rates of air movement .. 113

IX Air-Conditioning

General problems to be overcome; Unit air-conditioners;

Central air-conditioning - components and controls . . . 123

X Controls for Heating, Ventilating, and Air-Conditioning

Systems

Fundamentals, definitions; Control areas . 137

XI Heat Pumps

Definitions, basic circuits; Types . 145

vi

THE HISTORY. OF HEATING

The history of heating starts with prehistoric man kindling a fire

in his cave. He had no chimney, so he rushed outdoors occasionally to

clear his lungs of smoke.

The first thing he learned about fire was that it gave heat, and

heat could make his food more palatable and his body more comfortable.

Little good it did him though because early man did not know how to

start a fire when he wanted one. He could hardly adjust his need for

a fire to the eruption of a volcano or for lightning to set near-by

woods ablaze.

Finally man discovered he could start a fire when he wanted one by

rubbing two dry sticks together long enough. There were several varieties

of this method.

Perhaps the tost interesting one was the fire saw. A piece of dry

bamboo was split and filled with tinder. Another section of bamboo

was sharpened along one edge and used as a saw to cut through the first.

Hot sawdust dropping on the tinder set it afire. One day someone hit

a pyrite stone with a bit of flint. Sparks resulted, and man discovered

that if he caught the spark in a hit of dry tinder he had a fire.

Since none of these fire-kindling methods was very fast and most

of them uncertain, a fire once started was carefully ;warded. Almost

every village had a communal fire, and fire-tenders watched over them.

Eventually perpetual fires also were maintained in almost every

dwelling, and when such was the case the women of the home were given

the responsibility of "keeping the home fires burning". All this was

changed, however, when the first practical friction match appeared in

r-TA,

1827. These were known as Jones Lucifers.

Probably the messiest and most dangerous match appeared shortly

after 1800. Wooden splAnts tipped with a mixture of potassium chlorate

ard sugar was ignitad by dipping it into a bottle of sulphuric acid.

These were sold at 50 matches, including the bottle of acid, for

two dollars.

The "Jones Lucifer" was an obnoxius but practical match. It was

a wood splint tipped with a chemical containing antimony sulphide and

was ignited by drawing it through the folds of a special paper furnished

with the match box.

After man discpvered how he could start a fire when he wanted one,

he was confronted with the problem of what to do with it after he had

it started. Fire always is accompanied by heat and snoke. Man wanted

the heat but did not care for the smoke, but he had no way to keep

the one and discard the other. So for awhile he had both. Chimneys

were not used until early in the 15th century. They proved much more

efficient than a hole in the roof.

The tepee of the American Indian was a good example of this.

had an opening at the top through which the smoke could escape.

The Romans took the lead in heAing techniques and had a heating

system in more pretentious buildings that was not unlike some heating

methods used today. The ordinary method of heating a room in a Roman

house was by open fire pans or braziers in the center of the room.

Wood and charcoal were the most common fuels. Imported woods were

used for special occasions. The wood was soaked in water and then

drieC, and perfume added.

The average British family in the ancient days has one place for

a fire, and that was a hole in the center of the floor. Later a regular

hearth was constructed in the same location and still later the hearth

was moved to one side of the room.

Early Persians had a unique method of warming their buildings. They

provided an opening in the floor in the center of the room and sunk an

iron stove in the earth beneath it.

The most advanced method of heating in those days and for centuries

to follow was the Roman Hypocaust, which was a form of floor panel rad-

iant heating. The area of the building to be heated was erected over

a series of flues or heating chambers directly under the floor. The

furnace was a large circular or rectangular room with suitable arrange-

ments for burning the fuel, usually wood. The hot products of combustion

flowed into the underfloor heating chamber and then up a series of flues

on the inside surfaces of the walls.

Heating by the underfloor method was usually confined to the sleeping

quarters and to the baths, the latter being the favored rooms of the

Romans. This method of heating was only for the rich, and his less

favored brothers continued to use the open fire in the room.

In England and in some of the colder climates of Europe there

was much sickness and the prevalence of "consumption" or tuberculosis

gave rise to much concern. Most of these ills, it was asserted, was

the result of inadequate and uneven heating of the home.

When chimneys were invented, man made his first breakthrough in

separating heat from smoke. It was a step forward but mud') still

remained to be done. While he was able with the chimney to separate

smoke from heat, less that 20 per cent of the heat was used.

No one knows who invented chimneys nor precisely when they P.rst

3

appeared. There is some evidence that the remains of a chimney were

found in an English castle built in the 12th century.

With the coming of the chimney, also came the fireplace. This

was the principle method of heating for many years, not only in Europe,

but also in America. Wbod and charcoal were the universal fuels

through the 16th and early 17th centuries. The fireplaces were

inclined to smoke badly because of poor chimney design, particularly

if there was a lack of combustion air. This, in turn, was responsible

for heavy soot deposits on the inner passages of the chimney flues.

They had to be cleaned occasionally and thus was born the new trade

of "chimney sweeps".

Drafts of chilly air whipped across the floor and through the

room en route to the fireplace, chilling the backs of those seated in

front of the fire while the heat from the fire baked the front of them.

Although a number of improvements had been made in the fire place

over the years, it still remained an unsatisfactory method of heating.

Its successor was the stove. The early history of stoves is a bit

cloudy. The ancient Chinese had one made of brick. It retained heat

long after the fire had become a bed of embers, so it was used to heat

the rooms during the day and the top of it served as a warm bed at night.

Some old stoves heated two rooms instead of one° They were built

through a partition, with half in the living area and the other side

in the kitchen or servants' quarters where the firing was done. The

stove as we know it today started in the fireplace opening with the

front end projecting out a short distance into the room. The smoke,

after passing through a modified type of diverting flue, entered into

4

the fireplace chimney. Soon it was redesigned as

a free standing stove connected to the chimney

with a smokepipe and the front enclosed with

doors. Box stoves ware the prototype of the mod-

ern.stove. They were just what their name implies

a box-shaped stove made with cast iron tsides, top

and bottom. There was a fire door in front and a

smoke pipe connection at the back. The early

stoves were not very efficient because they lacked

heating surface, so the stove designers increased the heating surface

by using unique and ornamental designs. One model of the box stove

was known as the "Four O'Clock Stove". It was a small model that

was designed for heating a bedroom. The fire was started about 4 p.m

to take the chill-out of the bedroom.

Later in the 18th Century came the

Cannon stoves, so called because they were

round instead of square. They- were used to

heat meeting halls, churches and court rooms.

During this time the use of wood was giving

way to anthracite coal. A result was the good

old Baseburner with illuminated front and sides.

One feature of a Baseburner was that a

sufficient supply of coal could be placed to

The front and sides had windaws covered with mica

last an entire day.

so the burning coals cast a ruddy glaw. The coal was stored in a mag-

azine and the coals burned around the base of the magazine. That WAS

5

good in theory but improper design and vent-

ing of the magazine resulted in accumulation

of gas. The explosions which resulted were

somewhat disconcerting to the home owner.

A number of Asher stoves should be men-

tioned. One is the Air-tight stove, intro-

duced about the middle of the 19th century

and widely used until the early 19001s.

They had two doors, one at the base of the

stove for removing the ashes (they had no

grates, the fire burning directly on the

cast-iron base) and one higher up in the

front for tossing in the wood.

We usually think of a horse as a

"hay-burner" but there were stoves

especially designed for burning hay.

It had a rather unusual construction

and shape and the hay was introduced

into it in tightly would rolls through

a couple of tubes leading into the firebox. In the west, stoves were

adapted to burn buffalo chips, corn cobs, and in the Northwest one

that would burn sawdust.

Replacing the stove with a central heating system brought about

many big changes in family living, as well as in the architectural

6

arrangements of the house and the furnishings used, The central system

took that dirt out of the living area and placed it in the cellar. Better

furnishings, finer fabrics, lighter and brighter decor followed. At best

the stove never was a thing of beauty.

Also gone is an element of family life that resulted because the

stove could heat only one roam well. The old.parlor stove usually was

placed in the "settin' room" and since that was the only comfortable

room in the house, that was where the family gathered after supper

dishes were done, and played games, told stories or read until time to

retire.

Just when central heating systems first appeared is not quite clear,

not is it clear whether the first such systemS were warm air or steam.

Steam heating did not come into general use until about the beginning

of the 19th century. On the other hand, the stove was used to heat

most homes, along with the fireplace, during the 18th century, and

the word "stove" was rather loosely used with respect to its use.

Hot water central heating systems were developed during the early

part of the 19th century and came into general use about the the middle

of thai century. The forward march to better heating started in earnest

during the first half of the 19th century. By the middle of the 19th

century much of the problems had been overcome, and central heating

systems appeared in more homes as well as public buildings.

The first warm-air heating system using a furnace appeared in England

about 1792. It was described as one using a "Cockle stove" and a system

of pipes and flues to heat a large cotton factory. The Cockle stove to-

day would be called a heat exchanger, direct fired. The Cockle stove

7

was made of cast iron and constructed with thick and heavy walls -

top, bottom and sides, or in other words a cast-iron case to enclose

the fire. This case was called the cockle, and ih turn it was en-

closed in a brick casing with a minimum of 3 or h inches between the

inside surface of the casing and the cockle or heat exchanger, to

provide air circulation. Openings at the bottom of the brick enclosure

allowed cold air to enter. The heated air was conveyed in pipes and

flues in to rooms to be heated from the top of the enclosure.

The early warm air furnaces came in for much criticism of a sort

that unfortunately continued into the 20th century. The heating

surfaces of the stoves or heat exchangers within the furnace assembly

became very hot - 1,000 degrees or more. It was claimed that when

air passed over such high temperature surfaces, it deteriorated and

was not fit to breathe. Heating engineers went to work and came.up

with a solution that heating engineers of a more recent era have redis-

covered. The cast-iron case of the Cockle stove, which received heat

from the fire, was covered with cast-iron ribs projecting three or four

inches from the surface. These ribs increased the heating surface and

thereby reduced the temperature of it.

The first warm air furnace along present day lines manufactured in

the United States) it is believed, was in Worcester, Massachusetts; in 1835.

This was the start of a new industry in the country and it expanded

rapidly. By 1850 there were a number of them producing furnaces. The

industry grew rapidly between 1850 and 1900, but the mortality rate

of manufacturers was high. Along with the increase in the number of

manufacturers came new designs and some of them bordered on the fan-

tastic. One novelty in furnace design was the "combination heater"

8

that could heat part of the house with warm air and the rest with

either steam or hot water. The lower sections of these furnaces

were not much different from a straight warm air furnace, bub inter-

ppersed within the combustion dhamber and the radiator was a small

boiler. It was a most complex-looking affair.

The principal requirement of a mechanic installing these furnaces

iims that of a strong back. They were made of cast-iron and the manuface

turer did not spare the iron. Some of these furnaces for an ayerage

sized house of that day weigh as much as 1,500 to 2,000 poundCgick

some of the individual sections, particularly the radiators, 400 to

500 pounds.

Furnaces were rated by diameter of the fire pot and the cubic feet

of space it wuld heat. The rated capacity in cubic feet was arrived

at by a guess and-by-gosh method and the rated capacity for identical

furnaces made by different manufacturers would vary- widely. No one

knew haw to design or install a good warm air heating system, and for

a while it seemed that no one cared. Manufacturers engaged in a price

war. The construction of the furnace was downgraded and dozens of

manufacturers went broke, As a result, warm air heating had a dismal

reputation along about 1900 and it was evident that something had to

be done.

In 1906 the Federal Furnace League was organized with these

objectives:

1. To supply the home abundantly and properly with fresh air.

2. That to do this and elevate warm-air heating to the posi-

tion it rightfully deserved required a concerted effort

toward education of the dealer.

Not announced but a part of the plan was to use a uniform method

of arriving at the capacity ratings of gravity warm-air furnaces.

The seed for associations had been planted. As a result the

National Heating and Ventilating Association was formed in 1914. The

name was changed to National WarmAir Heating and Ventilating Association

and still later to the National Warm Air Heating and Air Conditioning

Association and it is still operating under that name.

Meanwhile, use of steel instead of cast-iron in the manufacture

of furnaces had been increasing. Eventually a number of manufacturers

announced steel furnaces and that started a trend away from cast-iron

to steel construction.

The pipeless furnace era was one that did the furnace heating and

industry no good. Almost from the beginning, a separate warm air pipe

or duct was brought to each room in the house to be heated. However,

about 1916 a new type of furnace was marketed. Advertisements claimed

it could heat an average house with a single warm air register and one

return-air inlet, even though the house had two stories.

It looked good on the printed material. Many thousands bought

these furnaces on the strength of the advertising - only to find out

that they did not heat as they were supposed to. The houses were

becoming more spread out and there was difficulty in getting air to

some of the more remote rooms. Forced circulation of the air through

the heating system was beginning to receive serious consideration.

The first general step in this direction occurred when a furnace

fan, placed upon the market about 1920 or 1922, was especially designed

for small and medium-sized furnaces. This type fan gave way in the

10

march of progress and the advancement to the centrifugal blower.

The accepted practice of locating warm-air supply registers in

the baseboard on an inside wall of the room was satisfactory when

the rooms were large. Trouble started when houses became small

during and shortly after World War II. The rooms in these houses

were small and usually had only one wall suitable for the placement

of much furniture. That same wall usually turned out to be the one

wall where the warr-air register was located and if the homemaker

wanted to place a large piece of furniture dlong that wall it was

just too bad. To meet this problem the register was placed six

feet from the floor and over the top of the furniture. It was

realized that this would not give satisfactory heating unless the

blower operated almost all the time when the weather was cold. That

was when C.A.C. (Continuous Air Circulation) was introduced and it

worked so well that it has become a standard adjustment for all

warm-air systems. About 1950 it was discovered that placing the

registers in the floor or wall beneath the windows and locating the

return air inlet near the ceiling would greatly improve the heating.

Thet was the start of perimeter heating.

The introduction of automatic heat with oil and gas brought about

many revoluntionary changes in the design of warm air furnaces. The

forced warm air heating system with its blower, ducts and registers

makes a natural distribution system for summer cooling equipment and

the industry knows it aad is doing something about it.

Steam and then hot water heating came into being because people

were not satisfied with the kind of heating they were able to get from

11

stoves and the warm-air furnaces in use at the time. At one time, steam

heating was used to some extent in residences but it never was a popular

heating method. Very little, if any, steam heating is used in the average

moderate-sized home today. Vapor heating is used today, but that operates

in quite a different manner.

Not too much is known about the early days of steam heating. It

probably got its start when the first steam generators were made to operate

the first steam engine. This was about the end of the 17th century. In

1769 Watts made the steam engine a practical machine.

The first steam heating system that we have on record was installed

in 171.12. It had a crude cast-iron boiler to which was connected copper

pipes with shuttered openings in the pipe to allow the steam to escape into

the room. It heated the rooms to a satisfactory level but also filled them

with steam and vapor.

The first system of indirect heating with steam was installed a few

years prior to 1800. Later, indirect systems using hot water instead of

steam appeared too. Along about 1800 the first high pressure steam heating

system appeared in England, using pressures as high as 130 pounds. The

first hot water heating systems that we knok about came into being about

1835.

The early designers of these systems were much concerned about the

weight of a column of water 30 feet high, pointing out that such a water

column terminated in a wooden hogshed would cause the hogshed to "vio-

lently burst asunder". Consequently they used wrought iron pipes with

.inch thick walls made to withstand 3,000 pounds of pressure. The pipes,

or tubes as they were called, were compactly coiled back over each other

and installed in a brick furnace in the secondary passes where they were

12

-

exposed to the hot gases on their way to the

chimney outlet and not to the direct-heat.

The radiator in those days was nothing

to delight the heart of the home-maker, nor

did they in any way appeal to the esthetics

of the building architects. They were tre-

mendous things - just an assembly of a large

coil of pipes usually partially enclosed but

not necessarily so. Great progress was made

in the design and construction of uoilers

during the next 50 years and by 1900 they were not far different from what

they are today. Greater attention was given each year to boiler economy

and to the importance of both direct and indirect heating surface inside

the boiler.

Meanwhile great improvements had been made in the design and fabri-

cation af steel boilers, and were preferred by many heating contractors

because they were lighter and occupied less floor space than their cast

iron brothers.

Today all but the largest sizes of residential heating boilers are

comparatively compact units that are attractive and can be brought into

the house as an assembled unit.

Aside from the design of boilers, the industry was faced with problems

concerning the distribution system. it lot of work went into the solution

of these problems and it was not until about 1910 that all of them seemed

to be settled.

Hot water heating systems also were in trouble around the turn of the

century. All of them were gravity circulation systems which meant that the

13

motive power for circulating

the water was the difference

in weight between heated

water and cold water. That

was not very much to go on

and was insufficient to over=

come much resistence in the

piping system. This took a

change for the better about

ROT WA'rEP.riVADIes-roR Nur EX PA NS! o fI

1-/tv4(<

COAL PIREO

1910 when the heat generator was invented. It was a device placed in the

circulating system. Equipped with a column of mercury, it would not per-

mit the water to spill out into the expansion tank until the pressure of

the system exceeded 10 pounds. This greatly increased the ability of the

water to circuiate through the sysbem and made the use of smaller pipes

possible.

Circulator pumps appeared about 1930 and they pushed the water through

the pipes with a positive force. The sluggishness of the system diSappeared

overnight. Encouraged by what the pump could do, heating men again turned

their attention to the radiation and came up with a long narrow and low

radiator that took the place of the conventional:baseboard in the rooms and

thus for the first time completely inconspicuous.

Early in the 19h0ls someone hit upon the idea of eliminating the radi-

ators completely by warming the floors or ceilings and let these warm areas

in turn warm the rooms. This was strictly radiant heating - something the

Romans had done with the old Hypocaust. The general idea was to embed hot

water pipes in the form of grids in the concrete of a slab floor or in the

ceiling. The trouble was that the floors got too hot, giving occupants

a severe case of the "hot foot" and the ceilings were so warm that the

rooms were oppressive. After a bit of research had been completed, the

proper temperatures of the floor and the ceilings, too, were discovered

and radiant heating with hot water became very comfortable.

We are not always giving good heating systems to the home-maker

because too many in the industry think that they must be competitively

"cheap". It is impossible to be "cheap" without cutting corners that

should not be aut. At any rate, it is a long way from the fire in the

cave with a hole in the roof to the regulated heating apparatus of today.

15

CHAPTER I

GENERAL

CHAPTER I

In the simplest terms, Energy is the ability to perform work. It

may exist in several forms, such as heat energy, mechanical energy,

chemical energy, or electrical energy, and may be changed from one form

to another. For example, chemical energy in a storage battery becomes

electrical energy flowing through a circuit that lights a lamp (light

energy and heat energy) or turns a motor (electrical and mechanical energy).

Though it may be changed from one form to another, energy cannot be created

or destroyed, so that the same relationships of energy transformation always

apply.

Heat, a form of energy, is a distinct and measurable property of all

matter. Heat cannot be destroyed but can be transferred from one substance

to another, always moving from the warmer to the colder substance.

Temperature is the measure of the intensity or level of heat. The unit

of temperature most commonly used is the degree Fahrenheit. One degree

Fahrenheit is 1/180 of the difference between the boiling point of water

and the melting point of ice under standard atmospheric pressure. On the

Fahrenheit scale, the boiling point of water is 212 degrees, and the melting

point of ice is 32 degrees. Other temperature scales are (1) the Centigrade

scale on.which the melting point of ice is taken as 0 degrees and the boiling

point of water is 100 degrees and (2) the Reamur scale, on which the me1tir-1

point of ice is 0 degrees and the boiling point of water is 80 degrees. Still

other scales, less commonly used, are the Kelvin and Rankine scales.

/// 1 9

One unit used to measure given quantities of heat is the British

Thermal Unit, more commonly known by its abbreviation BTU. The BTU is

the amount of heat energy required to raise the temperature of one pound

of water one degree Fahrenheit. Conversely, if the temperature of one

pound of water is reduced one degree Fahrenheit, one BTU of heat energy is

removed.

A unit of measurement of quantities of heat energy less commonly used is

the calorie. A calorie is the amount of heat needed to raise the temperature

of one gram of water one degree centigrade. In the field of heating and

cooling Che BTU is used rather than the calorie to measure quantities of

heat.

The rate of temperature change within a substance depends upon the amount

of heat energy added or removed within a given time. For example: If a pot

of water is placed over a low flame on a stove, it will eventually boil if

the temperature of the flame is greater than 212 degrees F. If the flame is

turned higher, say to around 600 degrees, the rate of transfer of a quantity

of heat is much faster and the water boils sooner. In both cases, the temper-

ature of the water is the same, 212 degrees F., when it boils. On the other

hand, if the flame is less than 212 degrees F. temperature, regardless of hou

long heat was applied, the water would never boil, it would get only as hot

as the flame. The same principles apply in temperature reduction. A boiling

pot of water will cool to room temperature if heat is entirely removed. It

will cool to room temperature faster if it is placed within the freezing section

of a refrigerator.

20

The same quantity of heat is removed, but in a shorter time.

These same principles are used in heating and cooling of spaces within

our schools. When the outside temperature is very low, we do not attempt to

raise the temperature of the classrooms by setting the temperature of the

heating units at the final desired temperature, but by setting it considerably

higher. Where air handling units are used for heating and cooling, rapid

changes in room temperature are made in either of two ways: (1) by rapidly

moving large volumes of air through the space at the desired temperature,

or (2) by moving smaller volumes of air through the space, hut with a greater

temperature difference between the existing temperature and the desired temp-

erature. Moving large volumes of air through a given space can be distracting

due to noise, drafts, disturbance of papers, etc. This is why the proper design

of any such system requires study and knowledge. The proper operation of any

system, within its design limitations, also requires study and knowledge. The

improper operation of these systems always produces an unsati§factory situtation

and, at times, danger to the building occupants.

The following chart shows some relationships of different forms of energy:

1 horsepower = 550 foot-pounds (ft-lb) per second

= 33,000 ft-lb per min

= 746 watts

= 2545 BTU per hr

1 horsepower-hour (hp-hr) = 1 hp for 1 hr

= 746 watthours (whr)

= 0.746 kilowatthours (kwhr)

= 2545 BTU

21

1 kilowatt (kw)

1 kilawatthour (kwhr)

= 1,000 watts

= 1.34 hp

= 1 kw for 1 hr

= 1,000 whr

= 1.34 hp-hr

= 3,415 BTU

1 British Thermal Unit (BTU) = 778 ft-lb

1 Boiler Horsepower

1 Ton of Refrigeration(also see Definitions)

= 33,478.8 BTU per hr (also see Definitions)

= removal of 12,000 BTU per hour

= removal of 200 BTU per minute

In order to make a study of heating, ventilating, and air-conditioning, it

is advisable to become acquainted with the-meaning of the following words

and terms:

AIR CLEANER - A device which removes air-borne impurities such as dusts,

fumes, and smokes.

AIR7-CONDITIONING - The process of treating air to control its temperature,

humidity, and cleanliness, and the distribution of the air in a given

space.

AIROMEYER - An instrument for measuring the velocity of moving air.

AIR WASHER - An enclosure in which air is drawn or forced through a spray

of water to cleanse and humidify it, or dehumidify it if it contains too

much moisture. This is one type of air cleaner.

BAFFLE - A plate or wall for deflecting gases or fluids.

22

BOILER - A closed vessel In which steam is generated or in which water

is heated.

BOILER HEATING SURFACE - That portion of the surface of the heating system

which has fluid being heated on one side and heat from fuel on the

other, the fluid then being circulated through the system. This surface

is measured in the side receiving heat. It includes the boiler, water

walls, water screens, and water floor.

BOILER HORSEPOWER - The Centennial Standard, established in 1876, defines one

boiler horsepower as follows: "It equals the evaporation of 30 lbs. feed

water per hour, from a feed temperature of 100 degrees F. to steam of

70 pounds guage pressure. This is equivalent to 33,478.8 BTU per hour,

or the evaporation of 34_5 lbs. of water at 212 degrees F." There is

considerable variance in the exact figures used in computation in different

text references; one uses the figure 33,478 BTU, another 33,500, still

another uses 33,465. Another method used to express approximate boiler

horsepower involves dividing the area of the heating surface (expressed in

square feet) by either 10 or 12, depending again upon the text reference

used.

BRITISH THERMAL UNIT - The quantity of heat required to raise the temperature

of one pound of water one degree Fahrenheit.

BY-PASS - A pipe or duct usually controlled by valve or damper, for short-

circuiting fluid flow.

CENTRAL FAN SYSTEM - A mechanical indirect system of heating, ventilating,

or air-conditioning in which the air is treated or handled by equip-

ment located outside the rooms served, usually at a central location,

and conveyed to and from the rooms by means of a fan and a system of

distributing ducts.

23

COMFORT ZONE - The range of effective temperatures in which most adults

feel comfortable.

CONCEALED RADIATOR - A heating device located within, adjacent to, or out-

side the room being heated which is concealed so that the heat transfer.

surface is not visible in the room.

CONDENSATE - The liquid formed by condensation of a vapor. In steam heating,

water condensed from steam; in air-conditioning, mater extracted from

air, as by condensation on the cooling coil of a refrigeration machine.

CONDENSATION - The process of changing a vapor into liquid by the extraction

of heat. Condensation of steam or water vapor is effected in either steam

condensers or in dehumidifying coils and the resulting water is called

condensate.

CONDUCTION - The transmission of heat through a material, such as metal, which

does not need to move in order to transfer the heat.

CONDUCTOR - A material capable of conducting heat. The opposite of an insulator

or insulation.

CONVECTION - The transmission Of heat by the circulation of a liquid or a gas

such as air. Convection may be natural or forced.

DEGREE-DAY - A unit used in specifying the nominal heating load in winter.

Sixty-five degrees Fahrenheit is the base used in figuring heat need,

since buildings will usually need heat only when the outside temperature

is below 65 degrees. For any day, the degree-days can be found by sub-

tracting the day's average outdoor temperature from 65 degrees F. For

'instance, if the average temperature is 37 degrees, there are 28 degree-

days for that day.

24

DEHUMIDIFY - To reduce the amount of water in the air.

DEW POINT - The temperature at which water begins to condense from air

containing a certain amount of moisture.

DIRECT-INDIRECT HEATING UNIT - A heating unit, located in the room or

space to be heated, which is partially enclosed, the enclosed portion

being used to heat air which enters from outside the room.

DIRECT-RETURN SYSTEM - A hot-water system in which the water, after it has

passed through a heating unit, is returned to the boiler along a direct

path so that the total distance traveled by the water is the shortest

feasible. Usually there are considerable differences in the lengths of

the several circuits composing the system.

DOWN-FEED SYSTEM - A steam heating system in which the supply mains are above

the level of the heating units which they serve.

DOWN-FEED ONE-PIPE RISER - A pipe which carries steam downward to the heating

units and into which the condensate from the heating unit drains.

DRAFT - Difference in air pressure which causes a movement of air.

DRAFT HEAD - (side outlet enclosures) The height of a gravity convector between

the bottom of the heating unit and the bottom of the air outlet opening.

(Top outlet enclosure) The height of a gravity convector between the bottom

of the heating unit and the top of the enclosure.

DRY-BULB TEMPERATURE - The temperature indicated by a standardized thermometer

after correction for radiation, etc.

DRY-RETURN - A return pipe in a steam-heating system which carries"both water

of condensation and air. The dry return connects above the level of the

water line in the boiler in a gravity system.

25

EFFECTIVE TEMPERATURE An arbitrary index which combines into a single

value the effect of temperature, humidity, and movement of air on the

degree of warmth or cold felt by the human body. The numerical value

is that of the temperature of still, saturated air which would induce

an identical sensation of warmth.

ELECTRICAL HEATING ELEMENT - A unit assembly consisting of a resistor,

insulated supports, and terminals for connecting the resistor to elect-

rical power.

ELECTRICAL HEATING UNIT - A structure containing one or more electrical

heating elements, terminals, insulation, and a frame, all assembled in

one unit.

ELECTRICAL RESISTOR - A material which produces heat when an electric current

passes through it.

FINNED-TUBE RADIATOR - A steam or hot water heat-distributing unit fabricated

from metallic tubing with metallic fins bonded to the tube. They operate

with gravity-recirculated room air and are designed for installation with-

out enclosure, or with open-type grills or covers, or with enclosures

having top, front, or inclined outlets.

FUMES - A broad term which includes all kinds of odors coming from smoke,

chemicals, and the like.

FURNACE - That part of a boiler or warm-air beating plant in which combustion

takes place. Also a fire-pot or fire-box.

GUAGE PRESSURE - Pressure in pounds per square inch above atmospheric pressure.

Guage pressure may be indicated by a manometer which has one leg connected

to the pressure source and the other exposed to atmospheric pressure.

HEAT - A form of energy which can be transferred from one material to

another when there is a difference in temperature between the two.

HEATING MEDIUM - A substance such as water, steam, air, or furnace gas

used to convey heat from the boiler, furnace, or other source of heat

to the heating unit.

HEATING SURFACE - The exterior surface of a heating unit. Extended heating

surface: Heating surface having air on both sides and heated by conduct-

ion from the prime surface. Prime Surface: Heating surface having the

heating medium on one side and air on the other.

HOT WATER HEATING SYSTEM - A heating system in which water carries heat

through pipes from the boiler to the heating units.

HUMIDIFY - To add water vapor or moisture to any material, such as air.

HUMIDISTAT - A device for the automatic control of relative humidity.

HUMIDITY - Water vapor within a given space.

HUMIDITY, RELATIVE - A ratio of the amount of water vapor in the air to the

amount that the same air can hold, at a given temperature. Expressed as

a percentage.

INCH OF WATER - The pressure due to a column of liquid water one inch high at

a temperature of 62 degrees Fahrenheit.

INSULATION - A material having a relatively high heat resistance per unit of

thickness, used to prevent loss of heat by conduction.

MANOMETER - An instrument for measuring pressures. A U-tube partially filled

with liquid, usually water, mercury, or a light oil; pressure applied to

one end changes the level of the liquid in the tube, and the change of

level is measured to find the pressure.

27

ONE-PIPE SYSTEM - A steam heating system in which a single pipeline

supplies heat to the heating surface and returns the condensate.

PANEL IlEATING - A heating system in which heat is transmitted by both

convection and radiation from panel surfaces to the surrounding air

and surface.

PLENUM CHAMBER - An air compartment maintained under pressure and connected

to one or more distributing ducts.

POTENTIOMETER - An instrument for measuring or comparing small electromotive

forces.

POWER - The rate of performing work; usually expressed in units of horsepower,

BTU per hour, or watts.

PSYCHROMETER - An instrument for measuring the humidity or moisture content

of the air.

PYROMETER - An instrument for measuring high temperature.

RADIATION - The transmission of heat through space by wave motion. Radiant

heat travels in straight lines. It does not need any material such as

air to transmit it.

RADIATOR - A heating unit exposed to view within the room or space to be

heated. A radiator transfers heat in straight lines by radiation, and

by conduction to the surrounding air which in turn is circulated by

convection; a so-called radiator is also a convector but the single

term "radiator" has been established by long usage.

RECESSED RADIATOR - A heating unit set back into a wall recess but not

enclosed.

28

REFRIGERANT - A substance which cools by absorbing heat through expansion

or vaporization.

RETURN MAINS - The pipes which return the heating medium from the heating

units to the source of heat supply.

ROOF VENTILATOR - A device on the roof of a building through which air is

removed.

SATURATED AIR - Air which contains as much water vapor as possible without

condensation.

SPACE HEATER - A self-contained heating unit used to heat a single room or

space. They may be classified as to type of fuel used, 'method of heat

distribution, and design features.

SMOKE - Carbon or soot particles which result from the incomplete combust-

ion of such materials as coal, tar, oil, and tobacco.

SPECIFIC GRAVITY - The ratio of the weight of a body to the weight of an

equal volume of water at some standard temperature, usually 39.2 degrees

Fahrenheit.

SPLIT SYSTEM - A system in which the heating and ventilating are accomplished

by means of radiators or convectors supplemented by mechanical circulation

of air from a central point.

STACK HEIGHT - The height of a gravity convector between the bottom of the

heating unit and the top of the outlet opening.

STATIC PRESSURE - Air pressure used to overcome frictional and other resistance

to air flow through a duct.

STEAM - Water in the vapor phase. Dry saturated steam is steam at the saturation

temperature according to the pressure, and containing no water in suspension.

29

STEAM (Continued) - Wet saturated steam is steam at the saturation temper-

ature corresponding to the pressure, and containing water particles in

suspension. Superheated steam is steam at a temperature higher than

the saturation temperature correspond ng to the pressure.

STEAM HEATING SYSTEM - A heating system in which heat is transferred from

the 11-Aler or other source of steam to the heating units by means of

steam at, above, or below atmospheric pressure,

STEAM TRAP - A device for allowing the passage of condensate and preventing

the passage of steam, or for allowing the passage of air as well as

condensate.

SUPPLY MAINS (STEAM) - The pipes through which the steam flows from the

boiler or other source of supply to the run-outs and risers leading'to

the heating units.

SURFACE CONDUCTANCE - The amount of heat transferred by radiation, conduction,

and convection from a given area of a surface to the air or other fluid

in contact with it, or vice-versa.

THERMAL CONDUCTANCE - The rate of heat flow through a given area of a body,

of a given size and shape within certain temperature differences.

THERMOSTAT - An instrument which responds to changes in temperature and which

directly or indirectly controls the source of heat supply.

TON OF REFRIGERATION - The removal of heat at the rate of 200 BTU per minute,

12,000 BTU per hour, or 288,000 BTU per 24 hours. A two-ton unit, for

instance, removes 400 BTU per minute. The term "ton of refrigeration"

is based upon the amount of heat needed to melt one ton of ice.

Ai

30

TWO-PIPE SYSTEM (STEAM OR RATER) - A heating system in which one pipe is

used for the supply of the heating medium to the heating unit and

another for the return of the heating medium to the source of heat

supply. In a two-pipe system each heating unit receives a supply of

the heating medium directly from the furnace.

UNDERFED DISTRIBUTING SYSTEM - A hot-water heating system in which the main

flow pipe is below the heating unit.

UP-FEED SYSTEM - A steam heating system in which the supply mains are below

the level of the heating units which they serve.

VACUUM HEATING SYSTEM - A two-pipe steam heating system which can be operated

below atmospheric piessure when desired.

VAPOR - Any substance in the gaseous state.

VAPOR HEATING SYSTEM - A steam-heating system which operates at or near

atmospheric pressure and which returns the condensate to the boiler or

receiver by gravity. Vapor systems have thermostatic traps or other

means of resistance on the return ends of the heating units for preventing

steam from entering the return mains; they also have a pressure-equalizing

and air-eliminating device at the end of the dry return.

VELOCITY - The rate of motion of a body in a fixed direction. In heating

systems it is expressed in feet per second. Velocity equals distance

divided by the time.

VENTILATION - The process of supplying or removing air by natural or mechanical

means to or from any space. Such air may or may not have been conditioned.

31

VISCOSIMETER - An instrument for measuring the viscosity of oil.

VISCOSITY - The measure of oil's rate of flow. It is determined by

the length of time required for a designated amount of oil at a

definite temperature to flow through a tube of standard size.

WARM-AIR HEATING SYSTEM - A warm air heating plant, consisting of a

heating unit enclosed in a casing, from which the heated air is

distributed to the various rooms of the building through ducts.

If the motive head producing flow deperids upon the difference in

weight between the heated air leaving the casing and the cooler air

entering the bottom of the casing, it is termed a gravity system. If

a fan is used to produce circulation and the system is designed especially

for fan circulation, it is termed a forced air furnace or a fan furnace

system or a central fan furnace system. A fan furnace system may include

air washers and filters.

WET-BULB TEMPERATURE - The temperature registered by a thermometer whose bulb

is covered by a wetted wick and exposed to a current of rapidly moving

air. It is used in measuring the humidity of the air.

WET-RETURN - That part of a return main of a steam heating system which is

filled with water of comiensation. The wet-return is usually below the

level of the water line in the boiler, although not necessarily so.

32

CHAPTER II

FACTORS DETERMINING HEALTH AND COMFORT

33

CHAPTER II

Many of the factors which must be considered in determining the

health and comfort of the students in the classroom include temperature,

humidity, air movement, odor, dust, and noise. Tn addition: we must

take into consideration the heat generated by the students and light as

well as the loss of heat through windows, open doors, roofs and walls.

Looking first at the room TEMPERATURE, we run into the question of

what is proper room temperature? This is always a controversial question.

A comfortable temperature is one which will balance the rate of heat

generation in the body and the rate heat loss from the body. Of course,

the lower the temperature of the room, the higher will be the rate of

heat loss. But the rate of heat generation is not so easily controlled.

It varies between individuals and between males and females and changes

with age. In practice, we must work with averages and adopt standards of

temperature, humidity, and air motion that gives the greatest comfort to

the greatest number of people. It is impossible to set up any one fixed

standard for comfort that will give universal satisfaction, especially in

schools'where there is so much difference in ages of those whom the

engineer is expected to serve. The person who reports the temperature

conditions is usually the teacher, who is older than the pupils in the

room. Since the rate of metabolism and heat generation decreases as a

person grows older, the teacher, generating heat at a lower rate, requires

warmer surroundings than does the younger people. The amount of insulation

varies, too. For example, girls generally wear a lighter clothing than do

boys.

if i 35

Different parts of the building are kept at different temperatures.

The following list of preferred temperatures should serve as a guide:

AREASDEGREES

Classrooms68-72

Offices68-72

Assembly Halls (when used) 68-72

Manual Training Rooms 65-72

Corridors 65-70

Gymnasiums60-70

Toilets60-65

Locker and Shower Rooms 76-80

Swimming Pools80-86

Open Air Room 60-64

Kindergartens 72-74

Kitchens66-70

Cafeterias and Lunchrooms 68-72

Due to the wide variation between individual teachers temperature

desires, many temperature controls are sealed, in that, adjustments either

require a special tool or the case must be removed. It would be a good

idea for the custodians to check the temperature in the room frequently

each day. Some schools have set up a chart for each room on which the

teachers or pupils note the temperature at stated intervals during the

day. Then the custodian can use this information to adjust the amount of

heat delivered. The temperature of classrooms should be taken somewhere

near the center of the room about 4 to 5 feet from the floor, at a point

which does not receive direct heat from the heating unit.

36

Automatic thermostatic controls, when properly set, will provide

fixed temperatures at all times. If the room gets too hot, the heat will

shut off. It is your duty to see that the automatic controls are in good

working order.

Open windows often affect the heating system. This practice

however is not desirable. There are two important factors to be considered

when using the windows as a "thermostat." If a room is warm and a window

is opened, the thermostat will respond to the cold air and deliver still

more heat. If this thermostat is controlling a "zone", hence all others

in that zone will be overheated to an extremely uncomfortable degree.

The second point is a matter of economy. Units are delivering unwanted

heat while windows are open to obtain cool air, resulting in excessive

fuel consump.Z-ion.

HUMIDITY

Humudity plays an important part in the comfort of school children.

The amount of water that the air is actually carrying, relative to the amount

it can carry is called relative humidity. A relative humidity of 30-60% is

satisfactory for classrooms with the most desirable range being from 40-50%.

Warm air carries more moisture than cold air. A temperature of 68° with a

relative humidity of 62% gives about the same feeling of.comfort as does

70° with a relative humidity of 47% or 750 with 15% more fuel, so relative

humidity is an important factor in heating costs. Modern heating plants

control humidity through the use of atomizer sprays or evaporating humidifiers.

ODOR CONTROL

Human body odors, cooking odors, chemistry lab odors, cloakroom odors,

shower room and other such odors are not toxic, but should be removed from

the building and replaced with new, clean air. The new air may be outdoor

37

air or air that has been cleared of odors by washing or some other means.

Regardless of how the odor-free air is supplied, the custodian uses his

ventilation or air-conditioning system to add to pupil comfort.

AIR MOVEMENT

No definite rules have been established for determining the flow of

air needed to maintain sanitary conditions in a classroom. It would be

well for those designing school plants to provide equipment that will make

it possible to move large volumes or outside air through the building, if

it seems desirable.

The provision and control or prover air motion throughout an occupied

space is one of the difficult problems of air handling. Air motion is

cooling and must be considered in determining comfortable temperatures.

It should be at a minimum in winter and a maximum in summer. In classrooms

it will be confined by practical limitations to 15-25 cubic feet per minute

per occupant.

DUST

The ease or difficulty of controlling dust may depend upon the location

of the school. Schools in such areas as New York or Illinois may have very

little dusts however, schools of the Great Plains and desert areas, constantly

experience problems with dust and often find it very difficult to control.

Any school located near unpaved streets or roads will find dust and dirt

filtering into the classrooms, which necessitates closing the windows. This

is uncomfortable during warm weather unless the school has other air-lconditioning

or ventilation, and of course, dust means extra cleaning work, as well.

NOISE

Noise Will have a decided effect upon students and their work. Schools

located near railroad tracks, jet airports, heavily traveled highways, or

an area of intense activity may find noises very distracting. Classroom work

38

may have to come to a halt while a jet takes off or a long freight train goes

by. Windows may have to be kept closed even in warm weather, which will then

call air-Lconditioning or ventilating units into use. The constant hissing of

steam from radiators, the hammering of steam pipes, and the sound of ventila-

ting or air-conditioning fans are noise problems which custodians are often

asked to try to minimize.

ACTIVITY

Custodians, as well as teachers, often forget what effect a classroom

full of children will have on the heating and cooling system. A human being

generates more heat than you may realize. Each child gives off from 240 to

400 BTU per hour, or as much heat as a 100 watt light bulb. This means that

if a classroom is at the proper temperature when the children come into it in

the morning, it will soon be too warm. An average class of 30 children can

raise the temperature of a room from 68° to 700 within an hour when the

temperature outside is 300. At these temperatures, the youngsters compensate

for35% of the heat loss of 21,000 BTU. When they leave for a 20 minute re-

cess, the classroom will cool off again. Unless the rooms are provided with

individually controlled unit heaters and ventilators, the custodian will have

to consider problems of heat control for each classroom.

CLASSROOM LOCATION

Classroom location is an important factor in temperature control. In the

Northern part of the state, classrooms located on the windward side of the

building will be as much as 100 colder than those on the opposite side.

This temperature difference is especially noticeable in older buildings. A.

room which faces South will receive more heat from the winter sun than one

which faces North. For example, on an average clear day in the wintertime,

the sun's direct radiation through the windows of a south classroom exceeds

39

48,000 BTU's per hour. The same school classrooms facing East receive

approximately 25,000 BTU's per hour in the morning. The classrooms

facing West, receive the same amount in the afternoon. Of course, rooms

on the East side of the building receive sun heat in the morning, while

those on the West are warmed by the afternoon sun. The story on which

the classroom is located also has an effect on the heating problem. A

center-story classroom is much better protected from extremes -If tempera-

ture than are those in the upper and lower stories.

CONSTRUCTION MATERIALS

Heat losses in classrooms will depend also upon materials used in the

construction. Glass blocks and large amounts of glass on the sun side of

the building cause the interior temperature to rise remarkably when the

sun is shining.

AMOUNT OF LIGHTING

Incandescent lighting fixtures produce heat. Every watt of electricity

used for light produces 3.4 BTU per hour. Thus, in a classroom with 4,000

watts of incandescent illumination, the lighting fixtures will produce

13,600 BTU per hour or 65% of the heat needed to maintain room temperature

when the outside temperature is 300 F.

All of these factors must be taken into consideration in planning for

temperature control. The variables make it difficult for the custodian to

maintain the classroom temperatures in a comfortable range.

40

CHAFTER III

HEATING SYSTEMS

Heating systems in schools may be classified into 6 general classifi-

cations:

1. Hot air

2. Hot Water

3. Steam

4. Radiant or panel

S. Unit

6. Combinations of two or more of these.

(See Figure I)

In the hot air system, air is heated on metal surfaces in the heating

unit and is carried to the room by gravity or by fan.

Some of the advantages of the hot air system are:

1. Heating or ventilation may be combined into one unit.

2. It is easily operated.

3. Does not require elaborate equipment.

4. Lends itself readily to humidification.

5. Usually so designed that fresh air can be introduced.

Some of the disadvantages of the hot air system are:

1. Open windows and air pressure affect the proper distribution

of heat.

2. The equipment is large and requires more space than other types.

3. Air ducts leading to rooms require more space than other types.

M 43

r.4

7

e

'

t4

E-4 4-3<4 g4

,7)

;. IQ}4041i'

,,444444t4 OA'4(:-1,0kktk4 4 tt

\04...klq111.1.F.

10tniTe,-

,_

CID

1-1

(

h. Air movement may be noisy if the air is moved rapidly or if the

heating ducts are full.

5. Odors and fumes may be transferred to all parts of the building.

6. Offers a greater fire hazard than other types.

7. Areas to be heated must be comparatively near furnace.

HOT WATET, SYSTEM (See Figure 2)

In a hot water system, water is heated in a boiler and piped to the rooms

by gravity or by forced circulation.

1. The large quantity of water provides uniform heat. It does not

cool off as quickly as steam oi; hot nlr.

2. The temperature can be maintained 2h hours a day.

3. Temperature can easily be controlled automatically.

The disadvantages of a hot water system are:

1. It requires larger radiators than steam system.

2. The area to be heated must be located comparatively near the

boiler room.

3. It requires a greater length of time to raise the temperature of the

building.

h. Greater damage results from broken pipes than in the case of steam.

STEAM HEAT SYSTEM (See Figure 3)

The advantages of a steam heat system are:

1. It is easily controlled.

2. Heat is evenly distributed,

3. It is economical to operate and to install.

h. The boiler need not be located near the area to be heated, although

it is desirable.

5. Large amounts of heat is conveyed in a small amount of liquid.

45

Flow Control Valve

Supply Main

Tridicator

HOT ATER SYSTEM

Air Cushion Tank

Water Feed Valve

Pressure Reducing Valve

."1"--- Return Main

Relief Valve

DomesticHot WaterPiping ToInternalHeater

TYPICALHOT WATER BOILEREquipped for forcedcirculation and year'round hot faucet water.

COIN AIR VENT

Circulator

c

ONE PIPE FITTINGS

ivrAIRCUSHION TANK

RELIEFVALVE.,/

FLOW CONTROL VALVEPUMP

Schematic one-pipe forced hot water system (closed system)

FIGURE 2

4 6

Equalizer Piping

Safety Valve

Water Feeder AndLow Water Cut Off

Blow Off Piping

TYPICALSTEAM BOILER

STEAM HEAT SYSTEM

-4------ Steam Supply Main

_i

Return Main

Try Cock

Steam Gauge

RADIA 'OR AIR VENT

MAIN AIR VENT

POP SAFETY VALVE

Schematic one-pipe gravity steam heating syslem

FIGURE 3

47

i

The disadvantages of a steam heat system are:

1. Radiators must deliver full output or be turned off completely if

they are not equipped with thermostatic controls.

2. The system must be kept in good repair to operate economically.

PANEL HEATING (See Figure 4)

Panel, or radiant heating, has not been installed to any great extent

in school buildings. It consistsof heated pipes or ducts embedded in the

floor, wall, and/or ceiling. It gives promise of becoming a very saldsfactory

means of heating certain school buildings. Panel or radiant heating is useful

in kindergarten rooms since it provides a warm floor for children who spend a

great deal of time on the floor. It provides uniform heat.

Some of the advantages of the panel heating system are:

1. A steady temperature.

2. Little temperature differential between the floor and the ceiling.

3. Warm floors.

11. Lack of violent drafts if windows are open.

The disadvantages of a panel heating system are:

1. Considerable time lag in heating and cooling.

.2. Leakages are hard to repair.

3. Floors may be too hot in cold weather for the comfort of children.

11. It softens the mastic and tile of resilient tile floors.

Electrical heating is also used in panel and radiant heating. It is

a method of growing importance.

Summer ain-conditioning requires a great deal of electricity. In looking

for a way to maintain the demand for electricity, the year round, many

electric companies are encouraging the use of electricity for heating homes

and schools. As they are offered lower rates, schools of the South are

using this medium to some extent. There are even some schools in the

48

)t 0:=11`P,4:14.114,Ve 4rtzt,7 '

r.7.4

0P-1

Northeast portion of the United States which are using electrical heat.

The advantages of using electrical heat are:

1. The cleanliness of the system.

2. Less custodial service is needed.

3. Lower initial costs since no boilers, stacks, or tunnels are

needed.

4. Low maintenance cost.

The disadvantages of using electricity for heating are:

1. It may not provide enough heat in colder areas.

2. The high fuel costs.

UNIT HEATERS (See Figure 5)

Unit heaters are simply heating units with a fan to blow air across

them. Heat may be supplied by three different means:

1. Hot water or steam.

2. Electricity

3. Direct fire from gas, oil

Unit heaters may be hung from the ceiling or placed on the floor.

Ceiling units are used primarily in industrial shops and gymnasiums,

where the fan noise is not too objectionable. They utilize either direct

fire or piped heat. Small electrical floor units are often used for

supplementary heat in offices, locker rooms, ticket booths, etc. The

operation of the fan is thermostatically controlled. In hot weather, the

fan may be used to move 'unheated air in shops.

HEAT PUMPS (See Figure 6)

Some schools within the State of Florida have had a heat pump installed

for either heating, cooling, or both. The principal of the heat pump and

mechanics of its use will be discussed in Chapter XI in the manual.

50

COMBINATIONS

One of the most commoncombinations is that of hot water or hot air and

steam in which air taken from outdoors is heated by means of steam or hot

water, either in the basement or in the classroom itself and then circulated.

A unit heater may be constructed to take air from the outside and off the

floor, heated, and circulated about the roam. This system permits control

of heat and ventilation in each room and eliminates the fan room, steam

coils, and supply ducts used with a central system. It is also possible to

control humidity with this system.

CHAPTER IV

HEAT GENERATORS

3O2.,/ 5 3

CHAPTER IV

HEAT GENERATORS

Heat generators maybe classified in several ways such as to type,

whether it is a central unit heater, and the construction whether it is

cast iron, steel, etc.

Steam and hot water boi/ers for heating are made of cast iron or steel.

Cast iron boilers are usually (1) of rectangular pattern with vertical sec-

tions and rectangular grate commonly known as a sectional boiler; or (2) of

round pattern with horizontal, pancake sections and circular grate commonly

known as a round boiler. Sectional boilers are usually used for heating

schools, while round boilers are more often used as hot water heaters.

Boilers may be classified in several other ways. The more cammon

methods of classification are as to pressure, material use, and design.

Boilers may be either high ot low pressure. In a high pressure system, as

it is usually defined, the boiler plant generates steam at a gauge pressure

exceeding 15 pounds. A low pressure system is one which generates pressures

of less than 15 pounds. A low pressure system is by far the most desirable

for school plants for the following reasons:

1. Low pressure boilers are cheaper to install and maintain.

2. Cost of repairs to piping and auxiliary equipment is less.

3. Low pressure systems are more essay operated and are less dan-

gerous.

h. Less space in the boiler room is required.

S. High pressure boilers must have an operator in the boiler roam at

all times, thus the operator is not available for other duties.

55

6. Low pressure boilers may be placed in full load operation more

quickly than high pressure boilers.

7. Low pressure systems require fewer accessories.

CLASSIFICATION OF STEAM HEATING SYSTEMS

Steam heating systems may be classified as to pressure, vapor, and

vacuum.

Pressure systems may be classified into the following types:

1. One pipe gravity systems.

2. Air return systems.

3. TWO pipe gravity return systems.

4. Condensate pump and wet return.

A one pipe gravity system is the gimplest way to distribute steam for

heating purposes, but at the same time, is one of the most expensive to

install because it requires large steam risers and lines which also require

large radiator valves. (See figure 5)

In this system, the steam and condensate both flow in the same line but

in the opposite directions and have but one connection to the radiator. The

radiator is so placed that the condensate leaves the radiator at the same

connection at which the steam entered.

The air is eliminated from the radiators and lines by air valves

placed at the coolest point of the radiator and large air valves at the top

of the drop where condensation returns to the boiler. The air valves are

automatic. They will allow air to leave the system until the steam or

water strikes them,then close so the steam or water does not escape.

56

As

SUPPLy-VA I-. V E

STGAm

VENT-VAA/E

DRyuvirrgiz Lui4E _RETURN

WATER LINS- .-. 11COUNTER FLOW

SYSTEM

ONE PIPE HEATING SYSTEM

(THERE ARE OTHER VARIATIONS)

57

FIGURE 5

The steam pressure required to operate this system may be anything

under five or six pounds of steam per square inch as there are no parts of

this system that it would injure.

An air line system is exactly like a one-pipe gravity system except

( that the air valves are left off the radiator and drops, and a thermostatic

air line valve is used instead. A system of small piping is connected to

those air line valves which lead to an air line pump in the boiler room.

The air line pump removes the air from the radiators and lines but handles

no water. This air line system may be operated without the pump if so de-

sired, by opening the air lines to the atmosphere, allowing the air to es-

cape. Care should be taken to close the large radiator valves tightly so

that the steam cannot enter thP radiator and keep the condensate from re-

turning to the boiler.

In a two pipe gravity system, smaller piping may be used, but a double

system is required. The steam is distributed in one line and condensation

is returned to the boiler in the other. Ordinary air valves are generally

used in the radiator drops of the return lines. Impulse check valves, when

used on the discharge end of the radiators,-give the best results. The

pressuie in a two pipe system should be as low as possible to insure a

complete circulation of steam; four or five pounds pressure will not injure

the system.

Py replacing the ordinary air valves with vacuum air valves, this

system may be operated under a vacuum. The vacumm is produced by building

up steam pressure and then cutting down the fire so that the whole system

remains hot with four or five inches of vacumm indicated by the boiler.

58

TWG PIPE DOWN FEED WITHCONDENSATE PUMP

MA IN STEAM SJPPL1 -*

DOWNpeer)StnpqRtS ER

S P PLYVALVE:

L,bowt4FEED I

R ETON IRiS

TOE Itrio STATITRAP

STRAINER.

CATE V4

1-

Co1,r145ATEP Lori P

C-14ECk. VA LVE

m=0. .7. W./KO almOM

FIGURE 6

tlIkT Poc g ET

WAT-Frt

FLoAr-rileamostsvric.TRAP

A. Condensation pump (See Figure 6) is required when part of the radia;

and return lines are below the level of the water lines in the boiler. in

this case, condensation cannot return by gravity. Therefore, the conden-

sation is drained into a receiver at atmospheric pressure and an automatic

condensation pump feed it into the boiler under pressure. An atmospheric

relief valve is placed at the top of the receiver for the elimination of

air and this system cannot be operated under vacuum. Ordinary air valves

are generally used on radiators, but by the proper grading of radiators

and return lines, the air valves may be left off the radiators and all air

eliminated through the atmospheric valve on the receiver.

B. A vapor system is very delicate and for that reason is very seldom

installed. It is simply a two pipe gravity system with special features

for the elimination of air. No air valves are used on the radiators or

drops of the returns, but a special dry return line is taken off the regular

return lines and is carried to the boiler room where an air exhauster is

used to discharge the air at or below atmospheric pressure. In this system,

steam pressure must be kept as low as possible, not to exceed eight ounces

at the most. If steam pressure should increase, the condensate would clog

the exhauster and stop the circulation of steam in the whole system.

C. The vacuum system of a complete two pipe system employs thermostatic

traps at the ends of steam mains and the discharge end of radiators.

Condensate is returned to the boiler by the use of a vacuum pumpswhich is

a combination air pump and water pump. This system is generally used where

long runs are required, sometime in buildings 1,000 feet or more from the

boiler room. Air is eliminated through the thermostatic traps in the

60

return lines and is ejected from the syster. by the vacuum pump.

Steam pressure should be held below 2i pounds at the boiler or the

.excessive heat in the steam will injure the traps. Care should be taken

in closing down this system and the vacuum pump should be allowed to

continue operation for some time after the fire is closed off. This will

prevent water hammer in the steam lines when the plant is started next

time.

BOILER PARTS AND THEIR USES

The custodian should know the various parts of his boiler and their

uses so that he will be able to understand their function and thereby

become a better operator.

Since there are many types of boilers as well as many types of

accessories on some boilers it is not practical to discuss them all.

The important parts are listed below along with their functions.

Safety Valves

There are three kinds of safety valves on steam boilers; the dead-

weight, the weight and lever, and the spring load. The deadweight

valve, as its name implies, is the direct loading of the valve with

weights. The ball and lever valve has the lever balanded on the valve

stem with an adjustable weight on the lever for variations of pressure.

The spring load valve usually has a pop valve which is held down by the

tension of a coiled spring, which can be adjusted to the desired pressure.

Safety valves are installed on all boilers to relieve excess steam

pressure. It is important that safety valves be tested once each day

the boiler is in operation to see if it is stuck'on its seat. If a

safety valve is stuck, the boiler must be operated by watching the

61

pressure very closely until it can he repAired or a new one installed.

To test the safety valve, pull the chain which is attached on the valve

lever so that the valve is lifted off the seat. If steam escapes, the

valve is clean and in working order. A valve leak can sometimes be

stopped by holding the valve open which will blow dirt off the valve

seat.

On low pressure boilers, the safety valves are set at 10 to 15

pounds. The safety valve on the section boiler which is held together

by stay bolts should be set to pop off at low pressure.

Pressure and Vacuum Gauges

The gauge most commonly used is called the Bourbon gauge, which

consists of an elliptical tube, bent into almost a complete circle.

The lower end is connected to the pipe where the pressure is admitted.

The other end is closed and attached to a lever which operates the shaft

upon which the hands or indicators are fastened. The hand Should always

be set at 0 when there is no pressure. If pressure is applied, the

tube has a tendency to straighten out which operates the needle.

Vacuum gauges operate in the opposite way: that is, when vacuum

has been created, the tube contracts and the hand indicates the number

of inches of vacuum. All such gauges should be checked often to deter-

mine whether they are operating properly.

Water Columns and Water Cocks

This arrangement usually is connected to the side of the boiler so

that the level of the water in the boiler is shown in the vertical tube.

It is always wise to drain the water from the water glass at least once

62

or twice a day. If the water does not rise quickly in the glass after

the cock has been closed, apparently there is foreign matter in the

indicator which prevents it from working as it should. It is also

wise to open the petcocks which are usually fastened to the side of

the indicator at three levels. Be sure that water drains out of the

cock below the level at which the water in the boiler should be carried.

It is also vise to open the others at intervals to be sure that they are

kept clean.

Check Valves

There are three types of check valves in general use in connection

with the heating system. They are the ball check, the lift check, and

the swing check. Check valves are used on water lines, or. in lines

where water must flow in only one direction. The check valves-open

to permit the flow in that direction, and close the pipe when the water

flows in the opposite direction. Swing valves are often used on boilers

and return lines where there is little pressure behind the water, because

these valves are almost evenly balanced and require very little pressure

to open.

Ball checks and lift checks require much more pressure to lift the

valve from the seat and aro not practical for this work, but they are

preferable for high pressure and compressed air. If a check valve fails

to.work, it should be taken apart and cleaned. If the seat is badly

damaged, it may be necessary to install a new seat, if possible, or

replace the valve.

FUSIBLE PLUGS

Fusible plugs are located on the crown sheet, in tube locations;

63

also at heads, fronts, and rears at eater levels. The indirect plug has

1 and 1/2 inch pipe and valve arranged and connected at the rear top

section of the shell extending to the interior surfaces above the tube

surfaces. The fusible plugs are often connected by the top opening of

the pipe on the exterior location of the shells, their purpose being to

relieve the pressure if the safety valve fails to operate. These brass

plugs have a hole drilled all the way hrough them. The hole Is filled

with pure tin or some other soft metal which melts at about 6000 F and

lets pressure blow off; this lessens the danger of boiler explosion.

FEED-WATER REGULATORS

These regulators automatically control the water supply so tRiet-the

level in the boiler is maintained at a constant level. They promote safety

and economy of operation and lessen the dangers of too little or too much

water. Uniform feeding of water prevents the boiler from being subjected

to the expansion strains that result from the temperature changes by the

irregular water feed. Thermohydraulic and thermostatic expansion-tube,

water-feed regulators are the two most common types.

BLOW DOWN APPARATUS

Water fed to the boiler contains impurities in the form of suspended

or dissolved solids. When the steam leaves the boiler, most of these

impurities are left behind. Some kettle to the bottom of the boiler while

others float on the surface of the water, so it is necessary to have both

surface and bottom blow-off lines on some boilers. Surface blow-off

connections may be stationary or floating. Both are used to remove oil

from boiler water. Such foreign matter as scale, kettiement, and rust

is removed from the bottom of the boiler by blowdown valves. Because hot

64

3RETAINEk

2STEM

VALVE ASSEMBI21

FOR

CONTROL OF WATER OR STEAM1

DIAPHRAGM

4

PACKING RINGS

5

CLOSE OFFDISC

7

PLUG SEAT

FIGURE 7

65

6

PLUG FORFLOW CONTROL

8

FLANGED BRONZEOR CAST IRON BODY

water and steam are harmful to the sewer, a separate blowoff tank is provided

from which the water is drained off into the sewer as it cools.

CARE OF THE BOILER

Most custodians know that the water level in the boiler should be

kept to a certain height. They know that the water level is supposed

to be checked in the water glass. They knowtoo, that dirty valves 1

leading to the water glass may prevent a true measure of the amount of

water in the boiler, and the good custodian tries these cocks several

times each day. The custodian also probably knows that if too much

water is put in the boiler, it will result in expensive operation and

if too little water is retained in the boiler, the crown sheet may be-

come dry and explode when water is thrown on it. Most boilers are set

so that 1/3 to 3/4 glass of water gives the hest rsults. 'If a boiler

.is properly set and the heating plant is correctly installed, there

will not be a great amount of water loss from the system. If there is

a loss of water, fresh water should be added as frequently as needed

to maintain the correct water level. A few plants drain ihe condensed

steam from all or part of the building into the sewer. It seems doubtful

that this wastage can be justified.

Pop or safety valves protect boilers from high pressures. The valve,

vibether a spring or a weight valve, should be set at the lowest pressure

practical as a maximum for the boiler. Test this valve daily. If it is

a spring valve, test it by pulling on this wire attached to the lever or

trigger; if a weight pop valve, test by lifting the weight lever slightly.

Boilers are equipped with a soft plug in the top of the crown sheet.

66

The soft plug serves the boiler as an electric fuse serves an electric

line. It is a weak point that will give way thus protecting the rest of

the boiler. If the boiler is free from scale, a soft plug may offer full

protection against explosions resulting from low water level. If the

boiler is permitted to scale, the soft plug may be coated until it will

not affect the boiler. If water does get below the safe level, shut off

the burner and let the boiler cool down before new water is added.

Air is admitted to the fire through a special secondary device. If

the quantity of air admitted is too great, the gases will be cooled below

the ignition point and will not burn.

Boilers are also equipped with check valves in the return mains and

in the water lines to prevent the pressure of the boiler from blowing

back through these lines. If the water is dirty, sediment may collect

in the check valves, preventing their working as they should. Check

valves have caps which may be taken off to facilitate cleaning.

67

CHAPTER V

FURTS AND COMBUSTION

The principle fuel used to heat Florida school buildings are gas, oil

and electricity. These fuels vary in quality, cost and abundance in dif-

ferent localities. The methods of firing furnaces will depend much upon

the type of fuel used. The furnace should be the type that is adapted to

use the fuel comnonly used in the region.

GAS

Gas has increased in popularity for heating homes, schools and facto-

ries and has to some extent replaced oil for heating Florida schools.

Since gas feeds automatically into the burner of the furnace, eliminating

storage, and since it burns without the residue or ash common to coal, mood

and oil, it has found ready acceptance in schools. There are a number of

gasous fuels, howeve; the only one used extensively in schools is natural

gas,

Nattral gas comes close to being the ideal fuel because it is free

from non-combustible gas or ash. Natural gas is found under pressure up to

2,000 psi. in porous rocks and shale formations or cavities. It is found in

more than 30 states and is transported by an extensire network of pipes to

nearly every state. It is 55% to 95% methane, with small quantities of

other hydrocarbons. In its natural state it is colorless and odorless, but

as a safety factor to detect fuel leaks, odor is mixed with it. Natural

gas may be classified as wet or dry, depending upon the amount of hydro-

carbons. Wet natural gas has more hydrocarbons than dry natural gas. The

heating value of natural gas is 950 to 1150 BTU per cubic foot. Oil is

often used as a standby fuel with natural gas in case of gas-line failure

or low pressure in the line due to excessive cold-weather demands for gas.

Manufactured _gases are not commonly used for heating schools. These

gases are blast furnace gas, sewage gas, coal gas, coke gas, and others.

Their heating range runs from 500 to 600 BTU's per cubic foot.

Liquified petroleum or bottled gases are occasionally used in heating

individual classrooms, or one-room schools far from a natural gas pipe line.

These gases, butane and propane, are made as by-products of gasoline manu-

facture. Both have high heating values, and since they are easily liquified

at low pressure, Alley- are often referred to as LP gases. Butane has a high

heat value - 3200 BTU per cubic foot - while propane's heat value is 2500 BTU.

FUEL OILS

A tremendous growth has occurred within the last 20 years in the use of

fuel oils :In our homes, scho31s and factories. In many areas, gas and fuel

oil furnaces have completely replaced coal fired furnaces. This is especially

true in the State of Florida. Today, very few schools, if any, are still

using coal fired furnaces. Fuel oil is a combustible liquid which is removed

from the earth as petroleum. Geologists theorize that the decomposition of

minute marine growths plus vegetable matter forms the oil that lies trapped

in pools between layers of the earth's crust. Crude oil, as the petroleum is

called when extracted from the earth, consists of 83% to 87% carbon and 10% to

14% hydrogen plus some traces of oxygen, nitrogen and sulfur.

Crude oil is removed from the oil wells to refinery mainly by pipe lines

and tanker. In the refining process, which employes various temperature and

pressure processes, the valuable products such as naphtha, gasoline, kerosene,

gas oil, asphalts, etc., are extracted by distillation and cracking.

72

Fuel oils are the petroleum products from which the most volatile elements,

such as the naphthas and gasolines, have been removed. Heavy fuel oils

are those with 86% carbon and 11% hydrogen; lighter fuel oils are those

with 84% carbon and 13% hydrogen.

FUEL OIL CLASSIFICATION

There are various ways by which fuel oils are classified. A common but

very unsatisfactory method is by gravity as measured by a hydrometer. Specific

gravity in degrees API (American Petroleum Institute) was found by dividing

141.5 by specific gravity at 60° F. and substracting 131.5 from this answer.

Gravity in degrees Baume is found in the same way, but specific gravity is

divided into 140 and 130 is substracted.

A much more widely accepted method is the one established by the United

States Department of Commerce. Its classifitations are:

Grade 1 - A light domestic oil (distillate) for use in burners requiring

a volatile fuel with a minimum flash point of 100° F.

(or 38°-40° Baume).

Grade 2 - A medium domestic oil (distillate) for use in burners fequiring

a moderately volatile fuel with a flash point of 100° F.

(or 34*-36° Baume).

Grade 4 - A light industrial oil for use in burners requiring low viscosity

with a flash point of 120° F. and requiring no preheating

(24*-26° Baume).

Grade 5 - A medium industrial oil for burners requiring a medlum viscosity

fuel with a flash point of 130° F. and requiring preheating

(or 18*-22° Baume).

73

Grade 6 - A heavy industrial oil with a flash point of 1500 P

(or 14°-16° Baume). Because of its high viscosity, it

must be preheated before it is burned.

Viscosity and Pour points. This is the relative ease or difficulty

with which an oil flows. It is measured by the time in seconds it takes

a certain amount of oil to flow through a standard sized hole in a device

called a viscosimeter. The two used in the United States are Saybolt

Universial and Saybolt Furol viscosimeters. Viscosity indicates how oil

behaves when it is pumped. The pour point is the lowest temperature at

which an oil flows. Lighter oils will flow at lower temperatures than

heavy oils.

Flash and Fire Points. The flash point of an oil is the temperature

at which it will give off vapors which will ignite with a pop but not keep

burning when they are brought in contact with a flame. It is desirable to

know the temperature tia which an oil may be raised before its vapors become

explosive. In preheating oils, the oil temperature must be kept 10 F.,

or more, below this flash point.

The fire point is the temperature at which an oil gives off vapors which,

when ignited, will continue burning. The fire point helps determine the

burning properties of oil, and also help determine if all the fuel is being

burned.COMBUSTION

Combustion is the chemical combination of substances with oxygen, which

releases heat. It is oxidation. Rapid oxidation or combustion requires at

least three conditions for completion: (1) it is necessary to have a combustible

material or fuel; (2) enough oxygen must be supplied to combine with the fuel;

and (3) heat is needed to begin the process of oxidation.

74

During the oxidizing process, the oxygen of the air, combines with the gas,

oil, etc., and passes off as carbon dioxide (CO2) or carbon monoxide (CO).

The energy of the fuel is rapidly released as heat. Some things burn more

readily than others, but nothing burns until it comes in contact with

oxygen. Vaporous gasoline mixes thoroughly with air and burns with an

explosion. Natural gas is mixed with air to produce an inflammable mixture

at the heating nozzle. Fuel oil, on the other hand, is a heavy liquid and is

vaporized so that it will mix rapidly with air.

Fuel will not burn without oxygen. Each atom of carbon in the fuel

must have two atoms of oxygen united with it at the ignition temperature in

order that it may be completely burned. Air is 79% nitrogen and 21% oxygen

by volume. The nitrogen of the air is of no use in combustion. As each

particle of carbon must be brought into contact with the oxygen before it

will burn, considerable air must be supplied in order to get complete combustion

The perfect air mixture for methane gas (the major element of natural gas) is

one pound of methane gas to 17 pounds of air. The amount of air required varies

with differeAt kinds of fuel. However, the perfect ratio is seldom reached

and so variations from the perfect air-fuel mixture must be made. In praf:tice,

a fuel may take 50 to 100% more air than the theoretically perfect mixture,a

since the air and gas streams must be brought together and heated somehow to

start and maintain iginition. An ineffective method of mixing will effect the

completeness of combustion: if too little air is supplied, only one atom of

oxygen unites with each atom of carbon to form CO (carbon monoxide) instead o

CO2 (carbon dioxide). The CO passes up the chimney unburned, and considerable

fuel is wasted. Too much air is not desirable either. Air is generally suppli

to the combustion reaction in two ways: (1) primary air is introduced with the

fuel, and (2) the secondary air is supplied to the flames coming off the fuels

75

The combustible gas in a proper mixture of air needs the third

element, heat, to produce combustion. The lowest temperature at which

instantaneous combustion takes place is the ignition temperature. This

is the temperature at which a fuel begins to burn.

The gustodianwho knows his fuel can learn to regulate his fire by

the appearance and nature of the flame. An extremely blue flame indicates

too strong an air mixture in comparsion to a bright yellow flame indicating

too little air for the fuel being consumed. This may require regulation

of air entering the burner or of the secondary air that passes into the

burner in order to burn the volatile gases and the carbon monoxide. The

wise custodian will ask the gas company for a flue-gas analysis for gas

fired furnaces. This will tell him if he is getting the proper combustion.

Visible snoke over a flame may- mean that some of the carbon and other

solids are not being burned. With gas and fuel oil, too rich a mixture"

causes poor heat yield and too lean a mixture does the sane.

By this time, the custodian will realize that fuel, air and temperature

are useless for heating purposes unless their heat can be harnessed. Here

is the place to consider the furnace with its burners and fire box, the

boiler and its flues to absorb the heat that is produced. Two basic types

of burners get the fuel in position to be burned.

In suspension or bui'ner firing, the proper proportions of air and gail

are combined to produce a combustible mixture. Burners for oil and coal

on the other hand, must prepare the fuel as well as mix it and this requires

fuel bed firing. Liquid oil:is sprayed to a vapor and coal is heated.

Within the combustion chamber, the fuel must be mixed with air and ignited,

and the resulting reactions between fuel and oxygen carried to a finish.

76

There are three primary fuel sources in use in heating modern schools;

gas, oil, and coal. In Florida, the primary fuel sources are gas and oil.

Burning gas

Even though it appears that gas is ready for combustion, the propor-

tioning mixing and burning of gas can be handled in several different

ways. There are several different kinds of burners which are described

Law pressure or atmospheric burners. These burners operate with

natural gas at a pressure of from 1/8 to h psi. They are used for

domestic heating and burn with alplue luminous flame. Multi-jet con-

struction provides the maximum mixing of gas and air at the available

pressure. Jets bring small streams of natural gas tothe discharge

opening in the burner'in front of the firing chamber. :The furnace draft

causes air to flow around the jets, and the gas-air pressure is burned

as it enters the furnace. Dampers help control the air supply.

High pressure burners. Because pipe lines carry gas at fairly high

pressures, iarger gas installations use burners operating under pressures

of fram 2 to 25 psi. Since gas-line pressures vary considerably, from

30 to.50 psi, regulators are used to maintain uniform pressure at the

burners.

High pre...sure gas burners are generally used for steam generation.

There are four types of high pressure burners:

1. The i°22.1211r_2!_rina_has an annular manifold located between

the air register and the furnace wall and surrounds the burner

opening. A series of orifices drilled around the intersurface

of this ring sprays gas at an angle across the air stream toward

77

the center of the buirner opening. The gas-air mixture then

enters the furnace through a curved throat opening, where

it burns with a short transparent flame.

2. The center diffusion tube burner has the gas head with its

orifices located in the center of the burner. It remains

in this operating position at all times. In this burner,

fuels can be burned either separately or simultaneously. The

gas leaves the burner tip in the shape of a hollow cone and

at a wide angle to the entering air. A diffuser plate

assures steady and proppt ignition, together with the proper

mixing of fuel and air for complete combustion. A flame of

this type is short, intense, transparent and well distributed

throughout the furnace. Oil may also be used in this burner.

3, A turbine gas burner uses revolving instead of fixed orifices.

Gas pressure causes the burner to rotate at high speed, which

mixes and.proportions the gas to the air stream. These burners

when properly operated and maintained have no visible flame and

provide almost constant temperature throughout the furnace.

When oil is used, the nozzle tip is moved forward through the

hollow center, and law-pressure steam is used to mgke the nozzle

rotate.

A tangential burner uses pulverized coal as its alternate fuel.

This burner has a wide, fiat-wedged shaped tip containing a

number of orifices.. Air is supplied by a forced-draft fans

Ignition takes place at the burner tip. Combustion is rapid,

because of high turbulence of air.

Gas safety precautions. For the safety of the building and

78

the occupants there should be a gas shut-off outside the

building, as well as an automatic shut-off in case of line

failure to guard against explosions. If there is a strong

smell of gas in the furnace room, do not carry lighted tobacco

into the room. Air out the room before checking for the gas

leak. In case of doubt, call the gas company at once.

BURNING OIL

Oil burners must proportift.-thb,Ifiel and air, as well as mixing them.

This may be done by atomizing the oil within the burner so burning can

take place within the combustion chamber. The atomization may be affected

in one of three ways:

1. Using steam or air under pressure to break oil into droplets.

2. Forcing oil under pressure through a nozzle.

3. Tearing an oil film into droplets by centrifugal force.

"Three T's" are important in oil combustion: Time, Temperature and

Turbulence. Time is required to pump oil from storage to the burner,

to ignite it, to burn it, and to pass through the stack in a gaseous state.

Tenperature refers to the temperature of the oil, the temperature of the

ignition firebox, etc. Turbulence is the action caused by the burner in

breaking un oil and the distribution of it in a.uniformly sized flame to

produce more uniform mixture conditions over the combustion zone.

For good burner maintenance, use only uniformly free-flowing oil

which is clear of sediment. Burners should be kept in good condition,

free from carbon build-up. 'In rotary-cup burners, worn rims cause poor

atomization. When shutting down a rotary burner, place the cups with a

flame shield. Worn nozzles whould be replaced in the mechanical burcers.

79

Oil is clean in both handling and burning, is uniform in performance,

more easily maintained, and the cost is usually lower than coal. Main-

tenance costs are considerably lower due to the fact that the fire burns

in suspension, thereby reducing the cost of brick and grate replacement.

The dirt and labor of handling ashes are eliminated. Fuel can generally

be stored underground outside the building giving additional space inside

for other purposes.

There are many brands of oil burners on the market, but only a feu'

differences in the principles involved.

in common use:

The 7-resst_strelmnizinburner is very simple in construction,

consisting only of a piece of pipe which carries the oil to the atomizing

tip. There the oil is mixed with air which creates a turbulent acfion,

breaking the oil into a fine spray in the combustion chamber where it is

bUrned in a conital or flat flames, the shape of the flame being governed

by the shape of the burner orifice. This burner is used in kilns, small

heat treating furnaces, under melting pots and occasionally,in small

boilers. Original cost is low and maintenance is negligible. Its use

more or less limited to lighter fuels. Operating pressures are two to

pounds. TI:Ay are designed to use No. 1 and No. 2 fuel oil.

The construction of the high-pressure atomizing burner is somewhat

similar to the /ow-pressure type. This burner can handle a much heavier

oil and it is even simplier in design and construction than the low pressure

burner. An air compressor is a necessary accessory, which adds to the total

cost, and the atomizing cost per 1,000 gallons of oil is higher in the long

run. The No. 1 and No. 2 oil, which is generally used is atomized at 100 psi.

Ignition is by electric spark.

Here is a description of those

is

seven

80

The high-pressure steam-atomizing burner is constructed like the

burners just discussed, steam being introduced, instead of air, as

an atomizing medium. The chief difference lies in the mixing chamber

(the chamber where the oil and steam meet prior to being introduced

into the combustion chamber). Two kinds of chambers are usedl'one an

outside mixer, and the other an inside mixer. The inside principle

affords better control. The outside, however, is somewhat simpler

and the nozzle tip can be cleaned more easily. Steam is introduced

at various temperatures according to the viscosity of the oil. Steam

must be dry, moisture coming in contact with the oil will create an

uneven, pulsating flame which wastes oil. This burner will enable you

to burn any fuel which can be pumped, as for example, tar. Cost of

this equipment is low' but the cost of steam production, loss of water

from the boiler feed, etc., must be included when computing operating

costs. Nozzles are extremely sensitive to pressure changes, carbon

formation, dirt, etc. A'minimum of 2i pounds steam to 1 gallon of fuel

is required.

The fire is started by means of a waste torch on the end of An iron

rod. Before starting a fire, open all the hampers and doors to allow any

accumulated gases to escape. The steam line should be blown also before

starting the fire. Always open the steam valve before opening the oil

valves. An efficient fire produces just a slight haze from the top of the

stack. The burner nozzle should be removed and cleaned periodically. A

manually operated oil burner should be watched constantly as the fire may

go out any time due 'to water in the oil, a dirty nozzle, or insufficient

steam pressure.

There is the mechanical pressure atomizing burner, also simple in

construction and low in maintenance cost. The oil passes through a tube

under pressure and then to an atomizing disk which breaks the oil into

minute particles, and from there to a tip made of a heat resisting alloy

where it is burned. This burner is capable of handling heavier oils and

is generally-used in large power plant installations of 300 H.P. upwards,

where operations are faitly uniform, After around eight hours of constant

operation, it is generally necessary-to change burners and to clean the

nozzle and tip. Due to its orginal.low cost, it is possible to have

three or more extra burners on hand. The atomizing cost is fairly law.

The 1102.12EI21.12LEmlamal: appears to be more complicated and has

considerabiymore parts than those previously discussed. We might also

add that the orginal cost is considerably higher. However, its flex-

ibility is practically unlimited and it is highly efficient. Despite

the fact that it requires more machinery, it is easily adjusted and

maintenance cost is law. It is a self-contained, compact integral unit

that can be installed at the fire box of any boiler and is hinged to

the boiler, making it a simple matter to inspect the burning end. The

oil is introduced through a hollow shaft passing through a cup, which

revolves at high speed, (approximately 35/60 RPM), causing the oil.to

atomize. Air is mixed in at this same point, creating a turbulence and

a flame that can be made short, bushy or straight shot, by a very

simple adjustment. It can be operated manually, automatically, or

semi-automatically as desired. When operated automatically, uniform

temperatures can be maintained throughout the building by- means of a

roam or building thermostat. Ignition is by a combination of an

electric spark and gas flame. It has a wide range of capacity in any

82

given size and can utilize heavier oils. This burner is widely used in

public buildings, hospitals, institutions, industrial plants, etc.

In the vaporizing burner, fuel oil is ignited either manually or

electrically and is then vaporized. Openings in the side walls of the

burner.admit the primary air which forms a rich mixture of air and oil

vapor in the burner. Secondary air is then admitted to complete the

combustion. Fuel oil is fed by gravity and the flow is either ON at

the rated capacity or OFF at pilot flow as regulated by the thermostat.

Most vaporizing burners are limited to one gallon of fuel oil per hour.

Vaporizing burners are generally used for water heaters, space heaters,

and furnaces.

AUTOMATIC CONTROLS

These controls have become an essential part of our heating,

ventilating and air-conditioning systems. Automatic controls respond

to variations in temperature, relative humidity, and pressure. They

operate individually or in sequence to provide the desired conditions

throughout the system. The control system consists of:

1. .A controller which measures such variables as temperature,

humidity, or pressure through thermostats, humidistats, and

pressure controllers.

2. A controlled device which reacts to the impluse received

from the controller by regulating a valve, a damper, or a motor.

3. A controlled agent, which does what the controlled device

directs. Such an agent may supply more gas, steam, or water.

In addition to these items, most control systems have auxiliary

apparatus such as switches, relays, gauges, pilot light and other

83

indicators for observing the operation of the system. The controls for

automatic fuel burning equipment are:

1. Operating controls, which start and stop the burner.

2. Limit controls which guard against unscife temperature,

pressure, or water level, to assure proper burner

operation.

3. Primary controls which provide for safe, start and

operating procedure of the burners.

Since most automatic controls are delicate pieces of equipment,

only an experienced custodian should attempt to'adjust them.

84

CHAPTER VI

DAILY PROCEDURES

Each day during the heating season, certain steps must be taken to

insure that you have safe, efficient operation of your heating plant.

Before the boiler or heater is started each day, the following steps

should be taken to insure a safe, proper start:

I. Check the fuel supply. Too often complaints reported to the

maintenance department for correction stem from the failure to

check this one item. You cannot expect any furnace to fire

which does not have fuel.

2. Check the water level in your boiler. Do not attempt to start

if the water level is too low or too high. If it is too lovei

bring the level up to the proper level. In no case, should you

fire a boiler which does not have sufficient water. If it is too

high, check your expansion tank. If the indicator shows that it

also is full, then you possibly have an air leak in the expansion

system, and/or possibly an automatic water make-up valve malfunction.

3. Check the fire box. Make sure that it is clear of all trash and

is not flooded with fuel or have other obstructions in it. Do not

fire a furnace until you have checked these three items.

Unless the custodian is especially trained, he should refrain from

handling the heating controls, as they are very delicate and easily damaged.

In most cases, it is a good policy for the Board to have a contract with a

control company manufacturer to regularly inspect and service the schools

heating controls or have especially trained maintenance men to make these

87

adjustments. In no case is the custodian to attempt to adjust heating

controls.

BLOWING DOWN A LOU PRESSURE BOILER

This job must be started while the boiler is in operation. No header

valve or return lines are to be closed. The operation of the entire heating

system must not be disturbed. Take the following steps:

1. Check the water level in the boiler.

2. Add fresh water very slowly as required.

3. If the water in the.boiler has reached the maximum level and the

steam gauge is at operating pressure, open blow-off cocks wide.

4. When the water in the boiler has reached one inch below lowest

safe water level, close blow-off cock.

S. Refill boiler to operating level.

6. Check leakage from blow-off pipe or valve, if possible. This

may be done by checking water level in the boiler at night and

comparing it the following morning.

This process blaws off or forces from the boiler all foreign matter

such as, scale, sediment, rust, etc., which will hinder its operation.

LOCATING BOILER TROUBLE

A complaint regarding boiler operations generally will be found to

be due to one of the following:

1. The boiler fails to deliver enough heat. The cause of this

condition may be: (a) poor draft, (b) poor fuel, (c) inferior attention

or firing, (d) boiler too small, (e) improper piping, (f) improper arrange-

ment of sections, (g) heating surfaces covered with soot, (h) insufficient

radiation installed.88

2. The water line is unsteady. The cause of this condition may be:

(a) grease and dirt in boiler, (b) water column connected to a very

active section and, therefore, now showing actual water level in the

boiler, (c) boiler operating at excess output.

3. Water disappears from the gauge glass. This may be caused by: (a)

priming due to grease and dirt in the boiler, (b) too great pressure

difference between supply and return piping preventing return of conden-

sation, (c) valve closed in the return line, (d) connection of the

bottom of the water column into a very active section or thin waterway,

(e) improper connection between boilers in battery permitting boiler

with excess pressure to push returning condensation into boiler with

lower pressure.

4. Water is carried over into steam main. This may be caused by: (a)

grease and dirt in boiler, (b) insufficient steam dome or too small

steam liberating area, (c) outlet connections of too small area, (d)

excessive rate of output, (e) water level carried higher than specified.

5. Boiler is slow in response to operation of dampers. This may be due

to: (a) poor draft resulting from air leaks 1.nto the chimney or breaching,

(b) inferior fuel, (c)- inferior attention, (d) boiler too small for the load

6. Boiler requires too frequent of cleaning flues. This may be due to:

(a) poor draft, (b) smoky combustion, (c) too low a rate of combustion,

(d) too much excess air in the fire box causing chilling of gases.

7. Boiler smokes through fire door. This may be due to:(a) defective draft in

chimney or incorrect setting of dampers, (b) air leaks into boiler or

breaching, (c) gas outlet from fire box plugged with fuel, (d) dirty or

clogged flues, (e) improper reduction in breaching size.

8. Low carbon dioxide. On oil-burning boilers, this may be due to:

(a) improper adjustment of the burners, (b) leakage through the boiler

setting, (c) improper fire caused by a fouled nozzle, (d) an insuffi-

89

ciant quantity of oil being burned.

ELTMINATION OF WATER-HAMMER FROM THE HEATING SYSTEM

The pounding noise which is sometimes heard in the heating system is

called water-hammer. When steam comes in contact with water which has

become trapped in low places in pipes or radiators, some of it is condensed

in such a way as to form a partial vacunm. This starts the water oscillating

back and forth and sets up a vibration in the system which may cause serious

damage. Sagged pipelines, defective or leaking steam traps, radiators low

on one end, and water too high in the boiler are frequent causes of water

hammer. Leaky joints are the most common result, but in extreme cases lines

may be broken or fittings ruptured.

The follawing suggestions may help you eliminate water hammer:

1. Locate the point where the water hammer is the loudest.

2. If it is in the Piping, test for the low poin with spirit level.

Adjust hangers so that the pocket will be removed and water can drain

back into the boiler.

3. If the trouble is found to be in one end of the radiator, level the

radiator by placing a block under the end.

h. If the noise appears to be in a radiator trap, cut steam off the

radiator and clean the trap. If necessary, replace either the

entire trap or the damaged parts.

THINGS TO REMEMBPR WHEN OPERATING A BOILER

1. See that the valves at the top and bottom of the'water gauge are

always open and operating.

2. See that the steam gauge cock is open.

90

3. The pet cocks on the water column are for testing the accuracy of the

gauge glass. Use them.

4. Valves to the heating system, both the supply and the return, must be

wide open.

S. In the brick set boiler, all spaces between the boiler and the brick

must be clear of false work, mortar, brick and rubbish.

6. The breaching must be tight in the boiler wall and chimney. See

that it does not extend into the boiler or into the stack and cut off

the draft.

7. Do not carry more steam than is necessary to heat the building.

8. Unnecessary pressure wastes fuel.

9. Shift weights in regulator lever to change steam pressure.

10. Brush out fire tubes as often as necessary to keep them clean.

11. At the end of the heating season clean and inspect the boiler

carefully so that it will be in condition for the next heating

season.

ECONOMICS IN HEATING

Conservation of room heat

This involves regulating not only the source of heat, but also windows

and doors to make sure that heat is not wasted. If no heat escaped, the

heating plant could be shut down after the building had once warmed. Heating

and ventilation are inseparably associated, but they are in opposition. The

more ventilation, the greater is the amonnt of additional heat need. Here

are some ways to conserve heat with little or no outlay of money.

1. When the roam become uncomfortably warm, turn down rediator valves

91

instead of opening windows especially fran the top. This economy

is particularly applicable when thermostatic controls are not

provided.

2. Windows should be kept well putt:led. A surprising amount of air

will come in around poorly puttied glass.

3. Occasionally children may-use leeward entranccs when the wind is

strong.

4. The amount of cold air brought in from the outside should not be in

excess 9f the amount needed.

S. If the window shades are lowered when the room is not in use, heat

will be conserved. All window shades in the room should be raised

or lowered to a uniform height.

In carrying out the fourth suggestion, it is obvious that when mechanical

ventilation is used, the.outdoor intakes should not be opened until the school

building is occupied and the intakes should be immediately closed after the

close of school.

Prevention of Fuel Wastes

The most common causes of fuel wastes are:

1. Loss in handling, both before delivery and later.

2. Gases and carbon passing up the chimney as smoke, due to incomplete

combustion.

3. Heat lost through radiation from the boiler. Insulation will reduce

this loss by as much as 80%.

4. Soot in the boiler, which cuts down fuel efficiency, since it acts as

an insulator.

5. Radiation. Savings of fuel can be obtained by using the right material

to paint the radiator. Gold, silver, or bronze will decrease radiation

92

25%; aluminum will decrease radiation 15%; flat wall paint will

decrease radiaion 7%; however enamel, will increase radiation

5%.

6. Scale, which lowers efficiency.:: Steel conducts fire heat five times

as rapidly as lime scale. If necessary, water should be treated

before use in the heating system to prevent formation of scale.

7. Inefficiency of boilers due to lack of repairs, they should be

kept in good condition at all times.

8. Excess air. This perhaps is the greatest 3ingle cause of fuel loss.

About )40% excess air is sufficient for the complete combustion of

average fuels. Excess air may be due to one or more of the following

causes: (a) fire doorsmay be fittedpoorly; (b) fire doors may be

kept open too much; (c) air may be leaking at dampers or breaching;

(d) boiler settings may be badly cracked; (e) bricks may be porous;

(f) chimneys may be'cracked or pitted; (g) drafts may not be properly

adjusted.

9. Improper draft, which reaalts in a lack of combustion, is very

important as a source of waste. It is important that the chimney

be properly proportioned. There is a tendency for architects to

specify a chimney which is too low. This fits in better with the

general appearance of the building, but it is an important cause of

heat loss. Plenty of draft is essential to the proper combustion

of fuel. This is not as applicable where gas and oil are the fuels

used. Check chimney dimensions by referring to the catalog of the

company which manufactures the boiler that is in use.

10. Rooms may be overheated.

93

11. There may be leaks in water or steam lines.

12. The combustion chamber may be too small or poorly shaped.

13. Unused rooms may be heated.

lh. Heat may be lost from uncovered steam lines.

15. Excessive evening meetings may be held.

16. Leaking steam traps.

Items two, seven and eight may be remedied in part by proper firing.

Fire the boiler according to directions given by the manufacturer or by

some reliable engineer.

Since soot in the boiler cuts down fuel efficiency, the heating strfaces

should be kept clean by brushing and scraping. Flues of solid fuel boilers

should be cleaned often enough to keep the surfaces free from soot or ash.

Gas boiler flues.and burners should be cleaned at least once a year. Oil

burning boiler flues should be examined periodically to determine when

cleaning is necessary.

Testing Safety Valves and Low Water Cut-outs

The only positive method of testing a low water cut-out is by duplicating

an actual low water condition. This is done by draining the boiler slowly

while under pressure. Draining is done through the boiler blowdown line.

Many heating boilers are not provided with facilities for proper draining,

this is an important consideration.

Many operators mistakenly feel that draining the float chamber of the

cut-out is the proper test. But this Particular drain line is only pro-

vided for blowing out sediment that may collect in the float chamber. It)

most cases the float will drop when this drain is opened, due to the sudden

rush of water from the float chamber. Every boiler inspector can tell you

94

of numerous experiences of draining the float chamber and having the

cut-out perform satisfactorily. But when proper testing is done by

draining the bOiler, the cut-out fails to function.

Failure of safety valves to work is usually due to a buildup of foreign

deposits that result in "freezing". This is an indication that the valve

has not been regularly tested or examined. One of the greatest causes of

foreign deposit buildup is a "weeping" or leaking condition. The only way

to be stire that a valve is in proper operating condition is to setup and

adhere to a regular program of testing valves by hand while the boiler is

under pressure. Also, any weeping or leaking valves should be immediately

replaced or repaired. This is important.

Low pressure (15 psi) safety valves should be lifted at least once a

month while the boiler is under steam pressure. The valves should be fully

opened and the tiilever released so the valve will snap closed. For boilers

operating between 16 and 226 psi the safety valve should be tested weekly

by lifting the valves by hand.

Boiler Compounds

In certain localities the water will pit the boiler within a short time.

Rain water is particulatily bad for most boilers, it is desirable to have

the water analyzed to determine if an harmful effect to the boiler may

result from use of the water available. It may be possible to test the

water and provide treJAment with boiler compounds which will prevent pitting

and corrosion. Almost all water needs some treatment. Boiler compounds

may be purchased in either liquid or powder form. Properly used they prevent

and eliminate rust, congestion, corrosion and soiling in hot water supply

systems for kitchens, shower and other areas and the heating system. They

95

stop pitting and galvanic action not only of the boiler but also of the

entire heating system. From ten to twenty five percent of fuel cost may

be saved as well as the time and mate,-ials lost in boiler replacements.

96

".0

CHAPTER VII

BOILER CARE

Cleaning the Boiler

Soot acculumation on the heating surfaces and gas passages prevent

adequate draft. Soot and scale accumulation. on boiler tube surfgces

lowers the rate of heat transfer from the gases to the water for steam

generation. Three sixteenths of an inch of soot is equal in insulating

effect to one inch of asbestos. Soot and scale are good insulators

thereby lowering the efficiency of heat exchange from the gases to the

water of the boiler units. This hastens the deterioration of metal

surfdces by the action of chemicals and heat. Therefore the surfaces

should be cleaned of soot and scale accumulation periodically. Complete

combustion and maintenance of combustion until gases come in contact with

the heating surfaces are essential to prevent soot formation. Minerals

in the boiler water should be removed by treatment with chemicals, heating,

and filtering. The boiler may be removed from service and the scale re-

moved mechanically, or with chemicals, as the condition of the surfaces

indicate.

Mechanical cleaners are used to remove scale from the boiler and the

water wall tubes. Cutters powered by small motors are passed through the

tubes. A hose connected to one end of the motor supplies steam, air or

water to the motor, and dlso enables the custodian to feed the unit through

the tube and Withdraw it when the cleaning is completed. In using these

mechanical cutters, take care that the cutters cut only the scale and not

the metal of the tubes. Use motors of dhe proper size. Bent tube boilers

are, of course, harder to clean than straight tube boilers. At best

9-g199

mechanical cleaning is difficult and tedious.

Chemical cleaners have proved very successful in cleaning boilers.

They are very fast compared to mechanical cleaners. Take a sample of the

tube scale and send it to a custodial supply house or a chemical company

which specializes in water treatment for boilers; ask them to analyze it

and help you choose the oorrect mixture of chemicals - an accelerator to

dissolve the scale, and an inhibitor to protect the metal.

Some of the scale can be removed by boiling out with an alkaline

solution similar to that for removing oils and grease. Other scale requires

an acid solution. Bydrochloric acid is often used with an inhibitor. Acid

cleaning requires a circulating pump and solution tanks, and temporary-

piping. After the acid solution has been circulated through the boiler

unit at the proper temperature by means of the circulating pump, it is

draimd off, and the boiler surfaces are rinsed wlth an alkaline solution

to neutralize the remaining acid.

Foawing is caused by dirt or oil in the water, an overdose of boiler

compound, water carried at too high a level in the boiler, or too high an

overload on the boiler. In case of heavy foaming, there should be a

complete change of the source of supply and treatment of the water, adequate

blawing-off of the sarface, and lower blow-off openings. The entire interior

surface may have to be given a thorough cleaning to eliminate the source

of foaming, and to eliminate all the oils and greases from the surface of

the water end. If you find that your boiler is foaming badly, it may be

necessary to drop the fire immediately so that all.of the water will not

leave the boiler.

100

Broken Tubes

If a tube breaks on a low pressure system during operation, it is

essential that this boiler be removed from service and that correct

procedure applied during the separation for closing down of non-operating

periods. After a boiler is removed from service, the punctured tube

is removed and a new one installed.

Flue Care

Flues should be cleaned as frequently as needed. If the boiler is

properly installed, flues may be cleaned with the long wire brush flue

cleaner. If the flues have been permitted to cake with deposits, it

will be necessary to use the flue scraper. Deposits in the flues retard

the conduction of heat through the flue to the water, and thus increase

fuel costs.

If the boiler room does not provide sufficient space for cleaning thy

flues, you may have to use a jointed or flexible rod. However, cleaning

the flues at best is a dirty job and it is desirable to have ample room

to do the work properly. Both sectional and steam boilers need flue cleaning

frequently if coal is burned. Flues in high pressure boilers may be cleaned

by blowing or by the use of a steam jet. Leaky flues may be plugged at each

end to stop the leak temporarily. In attempting to replace the flues, be

careful not to injure the plate in cutting out the old flue. The new flue

should be cut to the right length, inserted, expanded and beaded.

Flue Gas Anal sis

One of the most common heat losses is the loss of unburned flue gases

up the chimney. Often this loss is greater than all others combined

101

(radiation, convection and conduction). To analyze these losses by carbon

dioxide analysis, samples of flue gases are taken, with their representative

temperatures. This enables the custodian to find out how much heat is lest

up the chimney. There is a simple portable device which determines only-the

carbon dioxide in the flue gas. Since most custodians are not skilled

engineers, the local fuel company can be asked to make this check, especially

of gas and oil fired furnaces. Poor burning may be due to poor drafts,

wrong mixture, plugged flues, or soMe other.fault, and the fuel company

will be able to make the necessary recommendations.

Oil in the Boiler

If oil is found in the boiler, be sure to remove it regardless of the

time and labor required. Oil floating on the water will adhere to the

shell at the water line. If a boiler is under heavy load and surging (mourn,

oil will also cling to the top row of tubes. Then the oil will loosen the

protective scale and lay the 1netal bare for rapid oxidation, and the boiler

will be damaged by pitting. There is also danger of burning or bagging the

sheets if oil comes in contact with them.

The method recommerlded for removing oil is as follows: Remove manhole,

raise water level well above the normal position according to the size and

condition of the boiler, put in soda ash, start a slow fire and bring the

water to a boil for about one hour. Allow to cool, then drain boiler and

flush with a hose. Oil adhering to the shell and braces along the water

line may be removed by Scraping followed by a steel brushing.

ElagImIula

Always be on the alert for electrolysis and stop its action as soon as

possible by suspending a zinc bar in the water between the tubes. Then make

12

every effort to find the cause of the trouble. Electrolysis can be detected

by the appearance of the blisters formed. Blisters formed by electrolysis,

when broken, will be bright underneath and not rusty like those formed by

ordinary oxidation. This electric action can ruin a boiler in a surprisingly

short time.

Mineral Coating on.Platès and Tubes

There should be a light coat of scale or mineral deposit on the plates

and tubeswhich serves as a protective agent for the boiler. However, if it

becomes too thick, the same scale may act as an insulator and result in the

burning and blistering of the plates and tubes. In cases where the coating

is insufficient, it may be increased by feeding the boiler in the following

manner. Place the quantity of lime desired in a large tub or pail filled

full of hot water. Allow this to settle and become clean, then siphon off

the clear liquid and introduce it into the boiler.; Never under any circum-

stances, introduce lime in itg solid form into a boiler.

Manholes and Gaskets

Before removing a manhole or handhole to replace a gasket, be sure to

mark the position and ends of the yokes, bolts, and plate. When a new gasket

has been fitted, replace the parts in the same position as nearly as possible.

Often the yokes are sprung or the bolts worn and a change in their relative

position may produce leaks that are hard to control without strain or breakage.

Clean' the surface of the manhole and coat the graphite before replacing the

gasket. All handholes and manholes should be re.titightened after the boiler

has been in service a few days.

103

Preparing Boilers for the Summer Layup

If a boiler is to be out of service for a month or more it should be

emptied, 6pened and cleaned internally and externally. The boiler, and

breeching, which includes the steel parts of the furnace, deteriorates much

more rapidly when the boiler is not in operation than when it is. Nearly all

fuels contains some sulfur, sulfur combines with moisture in the presence of

air to form sulphurous acid, which corrodes metal.

To prepare a boiler for a complete cleaning, remove the non-combustible

materials from the furnace and ash pits, and clean the firebox and flues.

Then wash the boiler. Be sure that you have allowed adequate cooling time

before running water into the interior spaces of the boiler, orthe sediment,

scale, and sludge will bake on tAe surface requiring considerable labor to

remove it. If you can't wash out the inside right away, fill the boiler with

water while it is still warm. If it is filled to the top and the water is

heated to about 180 degrees F. and then allowed to 600ll the boiler will not

corrode or rust. However, if space is left at the top, the combination of

air, metal, and water will rust it at the water line.

After the boiler has been emptied, the handhole and manhole cover should

be removed, and the entire interior of the boiler should be washed out with

a hose with as much pressure as possible. Be sure to hit all the spots of

scale and mud on the heating surface.

Never crawl into a boiler unless there is someone on the outside to help

you. It is unwise to take an extension cord into a boiler; use a flashlight

or fasten a light on the outside in such a way that it will provide adequate

light.

If you plan to leave a boiler full of water, clean it on the inside first

104

and outside last. If it is going to stand dry, clean the outside first

and then the inside.

mu-J.13c rtyrieuliOu

The Pacific Boiler Company recommends that dirty water be drawn off

the boiler at the end of the heating season, which Should thus remove all

sludge and corrosive material, and new water then be added to the top of

the guage glass. This means that a boiler is not completely drained off

each year. It is wise to heat the new water to about 180 degrees F. to

drive off the dissolved oxygen and carbon dioxide which causes corrosion.

New boiler compounds should be added at this time.

The Dry Method

The Kewanee Boiler Company, on the other hand, recommends a complete

internal and external cleaning of the boiler in preparation for the summer

layup. They further recommend keeping the boiler dry over the summer if the

climate is dry enough to warrant this. Shallow pans of quicklime or silica

gel placed in the boilerwill absorb most of the moisture from the air and

help prevent corrosion. Keep the doors tightly closed.

Boiler rooms should always be kept dry and well ventilated. It is highly

recommended that you do not use a boiler for a paper or rubbish burner during

the summer.

The inside as well as the outside of the breechings should be throughly

cleaned and painted with asphalt paint. This paint is recommended because

it is cheap, acid proof, and provides good protection against rust and corrosion.

The fire side of the boiler should be oiled. Run an oil-saturated swab through

the tubes. During this cleaning process, the steam guage should be removed

and cleaned as well as the water gaage glass. Glass that has been discolored

105

by the action of the water can be cleaned by filling it half full of vinegar,

putting your fingers at each end, and running the vinegar back and forth. A

mild solution of hydrochloric acid is also satisfactory.

As you clean a boiler, watch for signs of deterioration and weakness.

Some of the more important conditions to watch for are: corrosion, bulging,

distortion of boiler plates and tubes, le;ky tubes and plates, leaky seams

and rivets, blisters on the various surfaces, sagging tubes, exterior corrosion,

embrittlement of the heavy scale, oil-accumulation, and pitting. These condi-

tions should be studied and remedied.

Discovering Boiler Troubles

Bagging is caused by overheating of the surfaces due to lack of water

over tube surfaces. It is also caused by overheating of the metal as a

result of scale, sediment, sludge, grease or oil accumulation on the metal

surfaces which prevent the heat flows from the gases to the water.of the

boilers. The pressure forces the metal outward. The non-homogeneous con-

struction of the material in the tube or plates and laminated conditions

will cause bagging of the surfaces under operating conditions of the steam

generators.

Blistering is caused by conditions similar to those of bagging, including

lamination and non-homogeneous material of the boiler and the accumulation of

oil and heavy scale on the metal surfaces of varying thickness and area.

Pitting is 'caused by corrosion, chemical action of the feed water,

accumulation of oil of acid nature; and the non-homogeneous condition of the

material of the tubes. To remedy bagging, blistering and pitting, remove the

oil and scale accumulation, treat the feed water and metal surfaces, provide

material suitable and adaptable to the water surfaces, change water supply

106

and apply correct operati:n procedures. Bags and blisters on the boiler

surfaces can be heated and hanmerets back to original form.

Pitting is prevented by providing treatment of the water to neutralize

corrosive elements; change of source of uater supply; frequent blowing down

of the boiler -water; elimination of the cause of pitting as various matetials

of construction de-aeration of feed watsr to the boilers and addition of

fresh water or maks up supply of feed water to the boilers.

The causes of leaky tubes are scale and soot accumulations causing

overheating; poor material and workmanship; expansion and contraction strains;

low water; incorrect operating procedures; and corrosion of the surfaces.

107

CAST IRON BOILER MAINTENANCE

DURING the course of a normalheating season the average steam

or hot water heating boiler is subjected

to a wide range of expansion and con-traction stresses due principally to thevarying demands for heat and conse-quently an intermittent rate of firing.

From this it might be assumed thatordinary cast iron would not be wellsuited for heating boilers because it is a

relatively brittle material that cracksrather easily. However, use of cast iron

over a great many years has proventhat it is a satisfactory material for low

pressure heating boilers, provided theequipment is given a reasonableamount of care.

There is a strong inclination to for-

get about the heating plant when theweather becomes warm enough to shut

down the bniler. The owner is likely to

say to himself that there is no need toworry when the boiler isn't being usedand that there will be plenty of timeduring the summer to check over theheating plant and determine if it is in

satisfactory condition for the nextheating season. But there are severalgood reasons why a complete check ofthe heating system is in order immedi-ately at the end of the heating season.Deterioration of the boiler and systemmay be much more rapid during theidle period than when it is in service.Also, if there is not adequate provisionfor expansion between the sectionsserious damage may result while theboiler is idle or when it is started up inthe fall. Moreover, any repairs neces-sary to place the heating system inproper operating condition for the nextwinter's use should not be put off orforgotten until cold weather arrives, asit may then be too late to make satis-factory repairs without unnecessaryexpense.

CorrosionAn accumulation of soot and ashes

left in a boiler often results in rapiddeterioration by corrosion. Most fuelscontain, among other impurities, somesulphur, a certain percentage of whichwill remain in the soot and ashes which

accumulate on boiler surfaces. Duringidle periods the soot and ashes maybecome moist as a result of the boiler"sweating" or by absorption of mois-

ture from damp air in the basement orthe boiler room. Under such conditionsthe sulphur combines with the mois-

ture to form st.i:. ..urous acid, resultingin serious corrosion of any metal sur-face with which it comes in contact,whether the surface be the boiler, stack,breeching or other duct work.

To prevent corrosion which may, in

extreme cases, eat entirely through thebreeching or other duct work in a sin-gle season, or damage the boiler itself,all metal surfaces should be thoroughlycleaned at the end of the heating sea-son. The firebox, gas passages and thesmoke pipe should be brushed out. Use

of a wire brush and vacuum cleanerwill help in doing a good job. By get-ting the unit clean, the chances of acids

forming is greatly lessened and theboiler surfaces have a much betterchance of staying dry. In cases wherethe basement or boiler room is quitedamp during idle seasons, precautionsshould be taken to prevent corrosionby painting the boiler surfaces with aprotective coating, or taking steps toremove the cause of the dampness.

Trash and debris should not beallowed to lie around the boiler. Suchan accumulation may corrode the

5

Clean all boiler surfaces to protect againstexcessive corrosion during the idle season.

44011011

USE THISTYPE OF

WIRE BRUSH

108

metal supports for the boiler to suchan extent :hat the base may begin togive way, resulting in niovement or

shifting of the sections. If this occurs,leakage at the push-nipples and at pipeconnections is very likely to develop.

Expansion Between Sections

After soot and ashes have been cc,m-

pletely removed from boilers of thepush-nipple type, a careful examination

should be made to determine whether

or not there is ample provision for ex-pansion between the sections. Tie-rods

may have been incorrectly installed so

that they hold the sections too tightlytogether. Or there may be a seriousbuild-up of rust growth between thesections. Either condition may result in

cracking.If the tie-rods of a push-nipple type

boiler were installed properly, one of

the following three alternate proce-dures was followed after the sections

were assembled:I. The solid nuts- used on the tie-rods

for drawing the sections together

were backed off several turns toallow ample room for expansion; or

2. The solid nuts were used in con-junction with compression washers;

or3. Split nuts were used instead of

solid nuts, which in turn, may have

been used in conjunction with com-

pression washers.Any one of the above alternatives

usually provide adequate allowance f or

expansion of the sections. Each boiler,

as installed, should have been treatedin one of these three ways. However,this practice is not followed in all cases

as a few plumbers and heating engi-neers do not fully understand the seri-ousness of leaving the tie-rods tight ona boiler. In fact, many of them feel thatthe tie-rods are necessary to hold the

boiler together.The tie-rods on boilers of the push-

nipple type are provid5A merely forconvenience in assembling the sections

and are not necessary to hold the boilertogether. The rods could, in fact, beremoved after correct assembly of the

109

sections and the boiler would be just as

safe for operation as if the rods re-mained in place. The tapered design of

the push-nipples, together with theground surfaces of the nipples and theopenings into which they fit, are suchthat when the sections of the boiler areproperly drawn together by the tie-rods, the joints will remain tight inservice even' though the tie-rods areremoved. They are left in the boilermerely for convenience in reassembling

the sections in case repairs at a laterdate require their use.

When leakage is found at the nipples

on a cast iron boiler, plumbers andheating contractors will frequently pull

up on the tie-rods to correct this leak-

age without first checking to determinethe cause. Where this practice is fol-lowed, the tie-rods should again beloosened after the leakage is stopped.

If the leakage recurs it is probablyevidence of rust growth or other for-eign matter between the sections.

Rust growth between sections ab-sorbs moisture from the air during theidle period, resulting in additional cor-rosion which often builds up until

there is no more room for expansion.

Then a further build-up of rust growth

will exert great pressures tending topush the sections apart. If movement

occurs, nipple leakage is very likely todevelop, but if the sections are held

Check tierods on push-nipple typeboilers to be sure there is provision

for expansion of the sections.

,g-. SPLIT SAFETY NUT

COMPRESSION WASHER7

tightly together, cracking is certain tooccur. To prevent such a condition acareful check for rust growth shouldbe made at the end of the heatingseason or whenever it is suspected. Ifany is found, the boiler snould be dis-mantled, thoroughly cleaned and thenreassembled, repacking with insulatingmaterial between the sections. takingcare one of the three methods for pro-viding expansion, mentioned above, is

used. A less desirable method for re-moving rust growth is by scraping be-

tween the sections with a hack sawblade.

In any case, the tie-rods should be

checked at the beginning of each idle

period to make sure that they are loose

and that there is ample provision forexpansion of the sections.

Boilers of the header and screwednipple type and some push-nipple typeboilers are not subject to damage from

rust growth between sections becauseof their design. At least one manufac-turer provides short tie-rods extendingonly to adjoining sections and in thismanner prevents the concentration ofstress on the end sections which mayresult when full length tie-rods' areused. Other manufacturers use sectionsso designed that the contact area withadjoining sections is small and anycorrosion products formed will tend toslough off instead of accumulating.

Internal Cleaninglf, because of leakage from the re-

turn lines or some part of the system,it has been necessary to add consider-able makeup water to the boiler duringthe heating season, or if the conditionof the water in the gage glass indicatesthat the boiler water has considerableforeign material in it, the boiler shouldbe drained and thoroughly flushed out.This can be done by removing theplugs in the front and rear sections andwashing the boiler through these con-nections. Washing in this manner willnormally remove any sludge or loosescale. However, if there is evidencethat scale has baked hard to the in-ternal surfaces, arrangements should

110

be made to have the boiler chemicallycleaned by a reliable company that hashad experience in this method of scale

removal.

Leave idle Boilers FilledAll idle cast iron boilers, whether

for steam or hot water heatirg. willdeteriorate less during idle pf:riods ifcompletely filled with watcr. Steamboilers should be filled at least to thetop of the water gage glass or prefer-ably up to the steam outlet connection.The boiler and system in hot waterheating plants should be left entirelyfilled.

Leaving the boiler entirely filled withwater will also prevent the possibilityof damage by overheating should someperson start a fire before the heatingseason, or early in the heating seasonwithout first checking the water level.

The only exception to the abovestatement that cast iron boilers shouldbe left full of water when idle, appliesto boilers of this type that are left idleduring the winter months in a locationwhere freezing is a possibility> Suchboilers should be left drailied and dry,preferably with the drain connectionsand other openings wide open so thatthe internal surfaces will dry out.

When boilers have been drainedbecause of a possibility of freezing, aprominent or easily read sign should be

Service all operating and protectivecontrols during the summer months.

placed on them to warn that they arenot to be fired until filled and properlyprepared for service.

Other Maintenance PracticesAn additional worthwhile mainte-

nance procedure is to further inspectthe boiler to determine that no cracksor leaks exist and that there are no airleaks in the breeching. Any cracked orwarped cleanout doors that requiresealing, repair or replacement, shouldbe marked for attention. The boilerand breeching should be made as airtight as possible for greater operatingeconomy when returned to service. Airleaks at boiler openings or in thebreeching waste fuel.

When the boiler itself has beenchecked, then all piping, joints andfittings in the steam and water linesshould be examined for leaks or seri-

ous corrosion. All leaks should berepaired and badly corroded parts re-newed before the next heating seasonbegins.

Return PipingIt is of utmost importance that all

return piping in connection with eithersteam or hot water heating boilers becarefully examined at frequent inter-vals, and the inspection of this pipingduring the idle season should be mostthorough. Leakage in return pipingcould put the boiler out of service at amost inopportune time, so this pipingshould be maintained in good condition.

The water level in the boiler shouldbe watched during the early part of theidle season to see whether any water isbeing lost. If so, and if the boiler isknown to be free from leaks, the returnpiping should be carefully examined todetermine where the water is escaping.If any portion of the return piping isburied, it is probable that the leak is inthat section. This buried section of pip-ing should then be subjected to ahydrostatic pressure test or dug up andexposed for an examination. All de-teriorated piping should be replaced,preferably redesigning the system sothat the piping will thereafter be acces-

111

sible for inspection. If the piping mustbe below floor level it is preferable thatit be placed in a trench with a protec-tive ccver that may be removed to per-mit examination.

In any case where piping is buried,whether leakage is in evidence or not,it is advisable to subject that pipingperiodically to a hydrostatic test to de-terrnine whether or not it is sound.

Service All ControlsDuring the idle period all operating

controls, such as the water glass, safety

or relief valves, low water fuel cut-out,emergency water feeder, pressure con-

trob and firing controls, including anyautomatic-firing device, should be care-fully gone over and put in good order.

The water gage glass is an importantdevice on a steam-heating boiler. The

gage glass connections should bechecked during each idle period to de-

termine that they are open and free so

as to give a true indication of the waterlevel.

Low water fuel cut-outs and emer-gency water feeders if used should bedisassembled and carefully checkedduring the idle summer months so thattheir proper operation during the nextheating season will be assured. Manymanufacturers of such controls havean established service whereby thistype of equipment may be returned tothem for checking and cleaning. De-pending upon the type of service ren-dered, the unit may be repaired andreturned, or replaced with a rebuiltcut-out. In either case, a completelyoverhauled and checked cut-out will beavailable for installation before thenext heating season.

If the boiler is so provided, theburner and all operating controlsshould be serviced during the idleperiod by a reliable organization to in-sure trouble-free operation when it isagain used. Special attention should begiven all parts of the electrical system.

Safety and Relief ValvesAs it is common practice to try the

safety or relief valves at regular inter-

vals while the boiler is in service, the

operator should know whether or notthe valves are in satisfactory operating

condition. If there is any question re-garding the action of the valves, they

should be removed and overhauled or

replaced.There are now available on the open

market, for use with hot water heating

and supply boilers, relief valves of atype that have been tested and ap-proved by the National Board of Boiler

and Pressure Vessel Inspectors andstamped as complying with the currentrequirements of the ASME Heating

Boiler Code. Such valves are rated inBtu discharge capacity of either water

or steam and are much more reliablethan the older type water relief valveswith which many boilers are equipped.

Serious consideration should be given

to replacing any existing non-codewater relief valves with the new-typevalves for greater protection.

Avoid Use as IncineratorsThere have been a number of cases

where serious damage to cast iron boil-

ers resulted when they were used forburning rubbish or used as incineratorsduring the idle months. Cast iron boil-

ers should never be used as inciner-ators, as there is a good possibility of

the cast iron sections cracking bedauseburning waste material often results in

flash-fires that cause sudden expansion

of the cold metal surfaces.

SummaryIn summary, the points that should

be observed at the end of the heating

season by the owner of a cast ironboiler are as follows:I. Clean all boiler surfaces, firebox,

ash pit, breeching and ducts to pro-tect against excessive corrosion.

2. Keep the boiler room dry and rea-sonably clean, taking care thatdebris, ashes, etc., are not allowedto accumulate around the boiler orpiping.

3. Examine the boiler for evidences ofrust growth between sections andcheck the tie-rods on push-nipple

112

type boilers to determine that thenuts have been hacked off severalturns, or that the rods are providedwith split nuts or compressionwashers.

4. Keep the boiler full of water duringthe idle season to prevent corrosionand protect against the possibility

of some person's starting a fire in adry boiler. The exception to this

rule is that idle boilers in locationswhere they may be subject to freez-

ing, should be left drained and dry.

5. Replace any cracked or seriously

warped clean-out doors and checkfor air leaks at clean-out openings

and at the breeching, for greater

operating economy.6. Examine all piping, joints and fit-

tings for corrosion and leaks, pay-ing particular attention to return

piping.7. Service or have serviced all operat-

ing and protective controls during

the idle season to assure their

proper operation during the heat-ing season. This includes the safetyvalves, the low water fuel cut-outand emergency water feeder, the

pressure control, and the fuelburner and all operating controlsused therewith.

8. Do not use idle cast iron boilers as

incinerators.9. Contact your insurance inspector

for his advice in the event repairs

are necessary. A cast iron boiler should not be usedas an incinerator. It can be cracked

by such abuse.

Mb

WO

-

il

CHAPTER VIII

VENTILATION

Ventilation ig a process of supplying or removing air by natural or

mechanidal means to or from any space. This implies that ventilation is

concerned with quantity of air, but for comfort and health we are concerned

with securing air of the proper quality rather than supplying only a given

quantity. Strictly speaking, we should use the term "air-conditioning"

rather than "ventilation".Air-conditioning is the process bywhich the

temperature, moisture content, movement and quality of the air in enclosed

spaces are maintained within specified limits.

There are six factors that determine the degree of comfort experienced

by the occupants of a school building. They are temperature, humidity, air

motion, odor, dust and noise.

Contrary to old theories, the variations in oxygen and carbon dioxide

content in the air are not too important; they are too small to be of

physiological concern even under the worst conditionE of normal human

occupancy. However, we are interested in odor, dust, and humidity control,

and so it is desirable to introduce a certain minimum amount of clean outdoor

air. The amount of fresh air which should be introduced into a classroom has

not been definitely determined but the location of the school building,

condition of the outside air, and the number of persons in the room are a

few of the factors which should be considered.

The regulations of the State Board of Education of Florida has established

the following requirements:

Instructional areas must have at least thirty air changes

per h'our for summer ventilation and two air changes per hour

for winter ventilation. In places of assembly, there must be

at least thirty air changes per hour for summer ventilation

and three changes for winter ventilation. Other spaces such

.gang toilet rooms, food labatories, kitchens, and other spaces

generating odors shall have at least four air changes per hour

preferably by means of exhaust. Exhaust systems from sources

of odor shall not be combined with other exhaust systems.

In addition, regulations require a minimum air space of 200 cubic

feet per person in all occupied rooms.

METHODS OF VENTILATION

At least four methods of ventilation, when proper design and

operation are provided, are desirable:

(a) window ventilation

(b) mechanical exhaust

(c) mechanical supply

(d) combination of the other three

There are several types of ventilating systems which might be classified

under the heading of gravity systems. The gravity system depends for air

movement on the fact that hot air is lighter in weight than cold air. This

system is economical to install and brings fairly good results under certain

conditions.

Window ventilation has the advantage of being the least expensive since

there are no ducts, coils, dampers, motors, or fans. If a window is open,

air currents will provide some air change. Window ventilation is used

extesnively in Florida and is coming into use again in colder climates

even though it was once almost abandoned. It works well if properly designed and

116

used, particularily if windows are on two sides of the room at different

levels. However, since teachers are busy people, they do not always get

the most out of this ventilation system. In the rooms that have direct

radiation heating systems, it is desirable to place window deflectors,

which may be made of plate glass, in the windows over the radiators so

that incoming air is deflected upward, thus preventing a draft on the

students and at the same time providing for a proper mixture of the hot

atr from the radiator with cold air brought in from the outside. The

practice of opening windows at the top and bottom may remove some of the

heat from the room, but it is not considered an economical method of

ventilation, since it removes the hot air from the top of the room

directly to the outside instead of mixing it with the cool air near the

bottom.

The mechanical exhaust system uses fans to pull air from the classroom

to the outdoors. Air is pulled into the room from cracks in windows or

through open windows. This is an excellent method to use for ventilating

a toilet room, locker room laboratory or kitchen, since undesirable odors

are pulled directly to the outside air. There can be little question that

the mechanical system is the most efficient when properly installed and used.

There are several methods of installing, duct systems. One is to

provide ventilation ducts from each room out through the roof. No duct

should serve more than one room. These ducts should be made fire-resistant

to prevent fire from spreading from one part of the building to another

through them. They should be in fire-resistant partitions and may be

collected in the attic into what is known as a plenum chamber where several

ducts come together and discharge through the roof in one vent. This system

117

is rather effective but is somewhat more costIT to install than certain

other systems.

A second system is what is known as ccoridor ventilation. Under

this plan the foul air is taken out of the classroom under the cloakroom

doors or through louvers and grills in the bottom of the classroom door

and into the corrid'or. The air then moves up through the building and is

taken out through ventilation ducts extending from the upper ceiling through

the roof. This system is cheaper to.install and has proven satisfactory

in some buildings.

The 1222112Elcalsloply system tempers the air supply of a room. Stale

air is pushed from the room by incoming fresh air. Varying degrees of re-

circulation may take place, ranging from 0 to 100%, depending upon tempera-

tu-i-e and air needs. Air is supplied through ducts either from one central

fan or from individual room fans. Air is supplied mechanically by unit,

forced warm air, or split system.

The unit ventilator combines heating and ventilating in the form of a

room radiator, which contains a motor driven fan, automatic controls, and

automatic dampers to regulate the amount of outside air to be admitted and

the amount to be re-circulated. They are generally placed under the window

to form a -warm air shield betwcen pupils and cold air coming off the window.

Their distinct advantage is that heat and ventilation may be controlled in

each room. Incoming air is filtered, but the filters must be cleaned

regularly, especially in first floor classrooms, for dust and dirt may be

pulled in by the fans.

Even though these systems are automatic in operation, the custodians

must start and stop the unit ventilators with the rest of the heating system,

must maintain a continuous supply of steam or hot water; and must service

118

the units regularly to insure their continuous trouble-free operation.

Forced warm-air systems are used only in small school buildings, in

which air may be forced around the room from the heating unit. A thermostat

controls the flow of air which is forced into the room around its periMeter.

Stale air is exhausted from the room from registers high in the wall.

The split krstem is a combination of forced warm air and direct

radiation. The air is warmed by thermostatically controlled steam or hot

water coils and is forced into the room by fans. Ait is pulled from the

room by a central fan and re-circulated. Additional heat is supplied, if

needed, by direct radiators in the room. The controls are elaborate and

complicated, so the custodian must be well trained to get the best results

from the least operating difficulty.

AIR CLEANING

Air cleaning devices removecontaminates from an air or gas stream.

They are available in a wide range of designs to meet various air cleaning

requirements. Atmospheric dust is a complex mixture of matter made up of

smokes, dusts, mists, and fumes which are generally referred to as aeroSols.

A sample of atmospheric dust gathered at any given point will generally

contain minute particles of materials that are common to that locality,

together with other components which may have had their orgin at quite some

distance, but which have been dispersed by wind or air currents. A sample

of atmospheric dust will usually contain minute quantities of soot and smoke;

silica; clay; decayed animal and vegetable matter; organic materials in the

form of lint and plant fibers; and metallic fragments. It may also contain

mold spores, bacteria, plant pollen and similar particles which may motivate

an allergy'aLtack on sensitive people.

119

Air cleaning devices are divided into two basic groups: air filters

and industrial air and gas cleaners. Air filters are ordinarily used to

remove contamination such as is found in outdoor air and are employed in

ventilation, air-conditioning, and heating systems. School custodians

will, in most cases, be only concerned with air filters.

Air filters can generally be classified into three groups, depending

upon their principle of operation as (1) viscous-impingement, or wet type,

(2) dry, and (3) electronic.

Viscous-impingement filters employ a viscous coated media such as oil,

or other adhesive, against which the dust particles strike and are then

held by the viscous surface.

Dry or semi-dry types are sometimes referred to as strainer or screen-

ing types of filters. The media generally consists of extremely small ele-

ments or fibers spaced closely together, so that the air stream must seek

a torturous and meandering path in its passage through the filter.

Electronic air filters utilize an electrostatic field.

Each type of air filter has certain advantages and limitations, but

the variety of designs which are available today provides an opportunity to

choose the filter having the characteristics best suited for a given appli-

cation. Sometimes it is desirable to use two or more filters in series,

especially if an abnormal concentration of dust is anticipated and if a

high degree of dust removable is desired. The wet or adhesive types of

filters are best suited for the removal of the larger size dust particles

and for handling high dust concentrations. A wide range of dry types of

filtering media are available and these are quite effective on the smaller

particles of atmospheric dust but generally must be serviced at frequent

intervals. They are particularly suitable for the collection of lint.

Unit filters generally have metal frames which are riveted or bolted

120

together to form a filter bank or section. The rate of loading of the

filter obviously depends upon the type and concentration of the dirt in

the air being handled and upon the operating cycle of the system. For

this reason, periods between maintenance cannot be predicted with certain-

ty. Manometer or draft gauges are often installed to measure the pressure

drop across the filter bank and thereby indicate when the filter requires

servicing. The manner of servicing filter units depends upon their con-

struction. Disposable types of filters are constructed of inexpensive

materials and are designed to be discarded after one period of use. The

cell dides of this design are usually a combination of cardboard and

metal stiffeners. The permanent type of unit filters are generally con-

structed of metal in order to withstand repeated handlings. Various

cleaning methods have been recommended for filters of this design, but

the most widely used procedure involves washing the filter with steam or

water to which has been added a detergent and then dipping or spraying

the filter with its recommended adhesive or oil. The excessive adhesive

or oil should be allowed to drain from the filter before it is put back

into service. In order to provide as uniform an operating resistance as

possible, it is sometimes advisable to use the rotation system of filter

maintenance, where large banks are involved. In this procedure a portion

of the filter bank is reconditioned on an established schedule.

The media used in dry types of air filters are usually fabric-like

of blanket-like materials of varying thickness. Media of cellulose fibers,

bonded glass, wool felt, asbestos, synthetics, and other materials have

been used commercially. The medium in filters of this type is frequently

supported by a wire frame in the form of pockets or v-shapec pleats and in

other designs the media may be self supporting. The efficiency of dry type

air filters is usually higher than that of the viscous adhesive type filters.,

121

however, the life or dust holding capacity is usually lower because the

dust tends to clog the fine pores or openings thereby causing a higher

rate of resistance rise.

In some designs of dry type air filters, the filter media is replac-

able and is held in-position in permanent metal cell sides. In other de-

signs the entire cell is disposed of after it has accumulated its dirt

load.

In school air handling systems which include air filters the respon-

sibility for checking, cleaning, or changing air filters generally falls

upon the school custodian. A thorough study of the operating instructions

supplied by the manufacturer plus periodic inspections is necessary to

estdblish the frequency of servicing the filters. Failure to do so, and

allowing the filters to become overloaded with dust and dirt can reduce

the air flow and efficiency of the system drastically.

122

g N,4,441,10,4011

100, 0,4.0.1.,14

CHAPTER IX

AIR-CONDITIONING

Man's comfort and progress have been greatly influenced by climatic

conditions. Artificial control of humidity, temperature, air motion, and

air cleanliness is termed Air-conditioning. As we know, air-conditioning

is accomplished in part through ventilation. Air-conditioning combines

ventilation with air cleaning, heating, cooling, humidifying, and effective

control of air in motion within an enclosure. Most people associate sir-

conditioning with summer air cooling, but this is not completely accurate.

Air-conditionin& is not seasonal.

This new feature of ventilating is already being used in schools,

especially in the warmer areas of the United States. Most new schools

being built in Florida today are being planned for 100% air-conditioning.

The term used in place of air-conditioning in some school is "climate control".

Air-conditioning is used to combat these conditions:

1. Temperatures that rise into the high 90's during the school

term.

2. Dust, which requires natural ventilation to be curtailed, and

demand an air washing system.

3. Outside noises which must be eliminated or controlled, such as

those from air fields or highways.

4. Discomfort due to summer heat in buildings used for summer training

programs. summer school programs, or enrichment programs.

5. Heat and humidity which must be controlled in rooms used for

scientific and athletic purposes.

6. Stale air which cannot be ad2quately replaced by natural ventila-

tion.

j;7/ 125

A group of complex factors affect the air-conditioning load. They

are: (1) heat transmission, (2) solar radiation or sun effects (3) people,

(4) light and power equipment, (5) ventilation air or infiltration, (6)

product load, and (7)miscellaneous.

Heat transmission is the heat flow through walls, floors, windows,

ceilings, and roof. It comes about from a temperature difference between

the inside air-conditioned space and the outside atmosphere. Heat flows

in if the temperature is higher outside. This unwanted heat must be removed

by cool air.

Weather conditions make up most of the heat transmission load in

conditioned spaces. Local weather bureaus forecast valuable information

on this subject. An operation engineer can use forecasts to plan operations

ahead. Insulating spaces or buildings against transmission loads reduces

the load on the air-conditioning equipment.

Large places, such as classrooms and auditoriums, filling with people

suddenly can add to the heat load sharply. The area to be cooled should be

brought to the proper temperature before people arrive. It is much easier

to hold conditions after a precooling period than it is to bring down con-

ditions by starting up a cooling system after people arrive.

Lights add very little heat to average spaces, but extensive lighting

and the use of oversized bulbs often make up a large portion of the load.

The lighting load can be estimated by multiplying the total watts by 3.4.

Infiltration or ventilation represents an important load factor. It

varies with weather conditions, people load, and building construction.

Tightness of doors, windows, etc., are important preventive measures.

The mechanical elements of an air-conditioning system are:

(1) a means of cleaning the air, either by direct contact with water

spray, by air filters, or by electrostatic precipitation;

126

(2) an air-conditioning chamber in which the air is cooled and

humidified or dehumidified either by direct contact with a water

spray or by surface cooling with an additional means for humidi-

fication;

(3) a means of eliminating all free water;

(4) a fan, usually of the centrifugal type, for moving the air;

(5) a re-heater, for adding heat when required for purposes of

controls;

(6) a system for air distribution which is free of local drafts.

Air-conditioning systems are either unit or central systemc.

127

(

.

UNIT AIR-CONDITIONERS

A room air-conditioner is a factory-made encased assembly designed

as a unit for mounting in a window, through the wall, or as a console.

It is designed for free delivery of conditioned air to an enclosed space

without ducts.

These air-conditioners are designed to control ventilation, air

circulation, air cleaning, and heat transfer, along with cooling and

maintaining temperature and humidity, in a single room. Such self-

contained air-conditioning or cooling units are generally below 15 tons

capacity. Unit air conditioners are widely used for administrative

offices in the public schools. They are usually restricted to hot-

weather operation and range from 1/4 to 1 1/2 tons refrigeration capacity.

These are usually designed to be installed in the lower part of a window,

although floor models installed in front of a w±hdow are also used. Most

window air-conditioners take the condensed moisture from the cooling coil

and spray it over the condenser surface and vaporize it, thus eliminating

the need for drain connections. It is possible to remove the equipment for

winter storage, or to use it for winter ventilation. EaCh of these units

must be cared for individually.

Most units have adjustable louvers or deflectors to distribute the

air into the room with satisfactory "throw and without drafts. When

the unit has only one deflector, all air is delivered in one direction;

when it has several deflectors, the air can be discharged in several

directions simultaneously. Discharge air velocities range from 300 to

1200 fpm with low velocities preferred in rooms where people are at rests

Many schools are mow utilizing equipment known as "Unit Ventilators",

128

44.100 01", , 004,4, :1,1A" ":,104".4 r

for cooling and heating individual rooms. Unit ventilators are not a

complete, self-contained, ain.conditioned assembly. While they incor-

porate almost all of the i:eatures normally found in room air-conditioners,

such as air mixing, ventilation, automatic controls, etc., they receive

their cooling and heating medium from a central source through insulated

plumbing. Thus, the unit ventilator is a combination of both types, the

ft unit" and the "unitary".

130

CENTRAL AIR-CONDITIONING

Central air-conditioning systems use "unitary" equipment such as

fans, coils, filters, etc., which are designed for assembly in the build-

ing, rather than at the factory. A central system usually serves several

roams, with individual controls for each room. Where early models were

generally represented by a one-piece, floor mounted, water-cooled unit,

today the equipment group includes floor, ceiling, and wall mounted models

both of one piece unitary design and of two or more sections remotely in-

stalled with inter-connecting refrigerant piping.

The term "unitary air-conditioner" now includes an extremely broad

range of equipment and, therefore, presents a difficult problem in defi-

nition and classification. The industry, through its group representative,

the Air-Conditioning and Refrigeration Institute, has recently agreed upon

the following definition of a'unitary air-conditioner:

"A unitary ain-conditioner consists of one or more factory-

made components, assembled on the site and normally include an

evaporator or cooling coil, a compressor and condenser combination,

and may include a heating function as tQell. Where such equiptent is

provided in more than one assembly, the separated assemblies are to

be designed to be used together."

Such a system generally is cheaper than several individual units and

may be placed in an out-of-the-way place, such as the basement or attic.

Ducts are generally used with a centralized air-conditioning system. Ex-

haust fans pull the desired amount of air from the rooms, and return air

fans replace it with "new" or cleaned air. Generally outdoor air is pulled

131

in and distributed to the rooms in specified amounts. The returned air

may be either heated cr cooled.

Capacities of units presently range from 2 to 75 tons with the top

limit subject to upward pressure in recent years. The industry has not

standardized on capacity steps within this range, and therefore, no se-

ries of standardized sizes is available. In the range of 2 to 7 1/2

tons, the industry presently builds equipment having capacity ratings at

almost every step above the 1000 BTUH increment. From 7 1/2 to 50 tons,

the steps are generally in the range of 2 1/2 to 5 ton increments.

No particular pattern has been established in the industry for ei-

ther the shape or arrangement of components for unitary air-conditioning

equipment. Thus, the designer has a relatively free choice within the

scope of equipment classification with regard to shape, size, and gene-

ral arrangement.

CENTRAL SYSTEM DESIGN COMYONENTS

The design of a complete air-conditioning system to produce a given

capacity at a stated operating condition can usually be accomplished by

a wide variety of component combinations. The following paragraphs are

intended to serve as a general description of the various components used

in unitary air-conditioning systems.

REFRIGERATION SYSTEM

The refrigeration system in a unitary air-conditioner includes the

following:

1. Compressor. Compressors e usually of the reciprocating or

centrifugal type. The rotary cam type does not have the capacity needed

in large systems and its use is usually limited to window units and other

132

refrigeration uses.

2. Cooling Coil. Cooling Coils are either direct-expansion type

evaporators or chilled-water coils for use with a water chiller.

3. Condenser. Condensers are of three types: water-cooled, air-

cooled, and evaporative-cooled.

Water-cooled condensers, although least expensive from a first-

cost standpoint, have lost favor due to water shortages and the fact that

they can freeze up in winter time.

Air-cooled condensers require no water, can operate at all sea-

sons of the year, and have no water-treatment problems.

Overall cost for evaporative-cooled condensers are comparable to

air-cooled condensers.

4. fais).1_1.device. Current design uses capillary tubes, constant

pressure Ithlves, and thermostatic expansion valves (adjustable or non-ad-

justable super-heat). No specific expansion device is particularly favor-

ed, each being used as the design situation warrents.

5. Refrigerants. Unitary equipment is currently designed for use of

Refrigerants 12, 22, and 500.

6. Water Chillers. Unitary air-conditioners designed for use with

a remote chilled-water cooling coil must include a water chiller.

7. iltftiatrALLELILla. Piping can be factory-assembled or in the

nature of piping with qiiick-connect couplings. The quick-coupling connec-

tions eliminate the need for field-fabricated joints, purging, and leak-

testing.

AIR-HANDLING SYSTEM

The aft-handling system includes the following:

1. Propeller Fans. Usually used in the cooling of condensers.

133

2. Housed Fans. Evaporator air systems, in general, and some con-

denser air systems, are designed for use with extensive duct work. There-

fore, evaporator air fans are almost always of the housed type.

3. Fan Motors, Fan motors must be quiet and dependable. Since

bertficing can be difficult due to location after installation, motors

frequently must be life-time lubricated.

4. Direct vs. Belt Drive. Propeller fans which rotate up to speeds

of 1500 rpm and below 30 inches in diameter are usually direct-drive.

Larger fans and housed fans are usually belt driven. Housed fans of the

larger sizes are almost exclusively belt-driven.

5. Filters. Both disposable and cleanable type filters are in use.

The filter is always located on the inlet side of the evaporator coil to

prevent dirt accumulation on the wetted coil surface,

CONTROLS SYSTEM

The controls system inclUdes safety devices, protective controls

and capacity control devices.

1. Safety devices. Since the unitary air-conditioner is a pressure

system, protection from excessive pressures must be provided. A high pres-

sure cutoff is always required to shut off the compressor if the head pres-

sure should rise above normal working limits. Protection from excessive

pressure due to fire is required in the form of a fusible plug or similar

device.

2. Protective Controls. The control system normally contains at

least some of the following protedtive devices to prevent damage to sys-

tem components due to abnormal operation:

a. Compressor Motor: Electrical operation overload protectiOn.

b. Compressor Motor: Electrical locked-rotor protection.

134

c. Low-Pressure Cutout: Prevent freeze-up, operation on low

charge0 and excessive oil foaming.

d. Fan Motor Overload: Electrical overload protection.

e. Wiring: Short circuit protection.

3. Capacity Controls. On larger units capacity Control is pro-

vided tp match flucLuating load conditions. This is accomplished by

one of saveral means, including multiple circuit systems, compressor

unloaders, and suction-pressure regulators. Head pressure control is

also used in this sense.

HEATING SYSTEM

Heating is-accomplished by steam or hot water coils When the unit

is used in conjunction with an auxiliary heating unit. A recent trend

'has been toward unitary design, inciuding a direct-fired heater as an

integral component. These heaters may be either gas or oil-fired, and

reseMble duct heaters in basic design.

CHAPTER .X

CONTROLS FOR HEATING, VENTILATING, AND AIR-CONDITIONING SYSTEMS

137

CHAPTER X

CONTROLS FOR HEATING VENTILATING ANr AIR-CONDITIGNING SYSTEMS

Present day standards of comfort ciibined with capacity and rapid

responsd.of nodern heating and cooling equipment make automatic controlss

an essential part of heating, ventilating, and air-conditioning systems.

These automatic controls respond to variables such as temperature, rela-

tive humidity, and pressure. They operate individually or in sequence to

maintain the desired conditions throughout the system and in the occupied

space. A factor that has made the subject of autamatic control somewhat

confusing has been the matter of terminology. Many different expressions

or words have sometimes been used to convey a single idea or concept.

This section, therefore, attempts to use and define the terms that are

most common and suitable so that they may be readily understood.

FUNDAMENTALS OF AUTOMATIC CONTROL

A control system consists essentially of (1) a controller, (2) a

controlled device; and (3) a source of energy.

A controller is a device which measures a variable condition such

as temperature, humidity, pressure, and liquid level, and produces a

suitable action or impulse for transmission to the controlled devices.

Thermostats, humidistats, and pressure controllers are examples.

A controlled device reacts to the impulse received from a controller

and varies the flow of the control agent. It may be a valve, damper,

electric relay, or a motor driving a pump, fan, etc.

The control agent is the medium manipulated by the controlled device.

It may be air or gas flowing through a damptar; gas, steam, water, etc.,

flowing through a valve; or an electric current.

The controlled variable is the condition such as temperature, humi-

iW139

dity, or pressure, being controlled.

Most control systems form a closed loop. That is, the controller

measures and responds to a change in the cnntrolled variable and actuates

the controlled device to bring about an opposite change which is again

measured by the controller. This system of transmitting information back

to its origin is known as feedback, and makes true automatic control

possible.

An open-loop system is sometimes employed in control circuits, but

does not provide complete control. An outdoor thermostat arranged to

control the flow of heat to a building in proportion to the load caused

by changes in outdoor temperature is an example. This system has no feed-

back. It depends for its operation on a pre-arranged relationship between

outdoor temperature and heat input to the building, and room temperature

has no effect upon the controller.

Control systems are divided into five main groups according to the

primary source of energy:

1. A self-contained system combines the controller and controlled

device in one unit and employs the power of the measuring system to effect

the necessary corrective actions The measuring system derives its energy

from the process under control without amplification from any auxiliary

source of energy, and may be of the "sealed-bellows" or "remote-bulb" type.

Temperature changes at the bellows or the remote bulb result in pressure or

volume changes of the enclosed media which are transmitted directly to the

operating device of the valve or damper.

2. A pneumatic system utilizes compressed air, usually at a pressure

of 15 to 25 psig, as a source of energy. This is supplied to the controller,

which in turn, regulates the pressure supplied to the controlled,device.

3. A hydraulic agIn utilizes a suitable liquid under pressure as the

source of energy. The pressure often is considerably higher than a

140

pneumatic system, but in other respects the systems are similar. Hydraulic

systems find their chief use in applications where large forces are

required for operation of the controlled devices.

4. An electric system utilizes electric energy, either low or line

voltage as the energy source. The electric energy supplied to the controlled

device is regulated by the controller either directly or through relays.

5. An electronic system also uses electric energy, but employe an

electronic amplifier to increase the minute voltage variations of the

measuring element to values required for operation of standard electrically

controlled devices. Measuring elements are usually of the resistance

type, but thermocouples also are employed.

In addition to the conventional controllers and controlled devices,

many control systems require auxiliary devices to perform various functions.

Auxiliary controls for electric control systems includes:

1. Transformers to provide current at the required voltage.

2. Electric relays for intermediate control, time-delay, etc.

3. Potentiometers for manual settings or remote adjustments.

4. Manual switches for a variety of jobs.

5. Auxiliary switches on valves and dampers for sequencing.

Auxiliary control equipment for pneumatic control systems include:

1. Air compressors and accessories, for energy.

2, Electropneumatic relays for controlling certain functions.

3. Pneumatic-electric relays for making or breaking electric

contact by air pressure.

4. Many types of pneumatic relays.

5. Positioning and switching relays.

6. Pneumatic and gradual switches.

Auxiliary control devices common to both electric and pneumatic

systems include:

1. Sequence controllers for operating a number of devices in a

pre-determined sequence for safe and efficient operation.

2. Clocks or timers for turning apparatus on and off at pre-

determined times, for switching from day to night operation, and

for other time-sequence functions.

CONTROL ARRAS

Areas to be controlled may be classified as (1) central, (2) zone,

and (3) individual room.

Central control uses only one controller for the entire affected area

which makes no provisionsjo: variations in exposure of different parts of

the buildings or different occupancy load conditions.

Zone control for any heating, ventilation, or air-conditioning system

is employed where it is desired to control, by one set of controls, the

heating or cooling effect in a number of rooms or areas, having similar

orientation or occupancy. For zone control to be successful, the require-

ments must be approximately consistent throughout the extent of the zone.

Zone controls alone may not provide satisfactory temperature conditions in

all rooms or areas within the zone because occupancy; lighting load, space

arrangements, and similar factors cannot always be predicted with

A combination of zone controls with individual room control in critical

areas may be necessary to achieve complete satisfaction.

Individual room control. The ideal temperature control system for any

building is one that promotes maintenance of the desired temperature in

142

eVery room at all times regardless of the location and occupancy. Indi

vidual room control is desirable in schools, hospitals, and offices.

The advantage of individual room control is in fuel economy and

comfort for the occupants.

143

CHAPTER XI

HFAT PUMPS

/K 145

CHAPTER XI

HEAT PUMPS

The term HEAT PUMP as applied to year-round air-conditioning system,

common*y denotes a system in which refrigeration equipment is used in such

a manner that heat.is taken from a heat source and given up to the conditioned

space when heating service is wanted, and is removed from the space and dis-

charged to a heat sink.when cooling and dehumidification are desired.

The thermal cycle is identical with that of ordinary refrigeration, but-the

application is concerned alike with the cooling effect produced at the

evaporator and with the heating effect produced at the condenser. In some

applications, both the heating and the cooling effects obtained in the

cycle are employed simultaneously.

The teat-pump principle is also applied for purposes other than air-

conditioning, such as: supply of domestic hot water in residences and commercial

buildings, recovery of low-temperature heat as a useful by-product in industrial

operations, and disposal of heat from processes involving evaporation of water

or ether fluids at depressed temperature and pressure. Deffosting of evaporator

coils in refrigerating systems by intermittently admitting hot gas directly from

the compressor is another application of the heat-pump method.

Even though the heat-pump principle is not.new, extensive use of this

principle in practical devices has been accomplished only within the past twenty

years. Large central heat-pumps of modern design, within the capacity range of

about TOO to approximately 1,000 horsepower of compressor-motor rating, are now

operating in a substantial number of buildings.

Compressor types employed in large central systems vary from one'large

centrifugal unit to as many as eight multi-cylinder reciprocating units. A

single or central system is generally used throughout the building, but in some

)(A/ 147

-

AIR COIL

HEAT PUMP SYSTEM

ATER COILS

IBRATIONELIMINATORS

-

FIGURE 9

148

-

WATER PRESSURECONTROLS

COMPRESSORREFRIGERANT

ELECTRICALHOOKUP

instances the total capacity is divided among several separate heat pump

systems to facilitate zoning. Both well water and air are used as heat

sources. Compression is accomplished in two stages for a few recent projects.

Frequently, provision is made for heating and cooling to be supplied

simultaneously to separate zones of the building.

BASIC CIRCUITS

Fundamentals

Since, from the refrigeration standpoint, a heat pump is similar to

a conventional refrigeration system, its basic circuit may be represented

by Figure 1. Changeover between heating and cooling services may be accomp-

lished by: (a) actuating valves in the refrigerant lines, so as to interchange

the positions of heat exchangers constituting the evaporator and condenser,

respectively, in the refrigerant flow circuitry, or (b) by switching the

paths of air, water or other fluid that convey heat from source to evaporator

and from condenser to sink, respectively. The interchange function inherent

in heat-pump control led to use of the term reversed-cycle

during the early development period of the heat pump, but this inaccurate

name is now obsolete.

Heat of Compression added to gas

Low Pressure Saturated Gas

Hot In

Heat addedto refri-gerant bysubstancecoole

Cold Out

Compressor

Evaporator or CoOler

Expansion valve for

Reducing Pressure

High Pressure Superheated Gas

fCondenser

(......)

High Pressure Saturated Liquid

149

Cold In

Heat taken fromrefrigerant bycondensing medium

Hot Out

HEAT PUNP TYPES

Heat pumps for air-conditioningservice may be classified according to:

(a) type of heat source and sink,

(b) heating and cooling distribution fluid,

(c) type of thermodynamic cycle, 4

(d) Type of building structure, and

(e) size and configuration.

The more common types are shown in Table 1.

The air-to-air type is the most common type of system. It is par-

ticularly suitable for factory-builtunitary heat pumps and has received

favorable acceptance for residential and commercial applications. The

first diagram in Table 1 is typical of the refrigeration circuit employed.

A few installations have been made where the forced-convection indoor

heat-transfer surface has been replaced with a radiant panel.

In air-to-air heat pump systems, as shown in second diagram of

Table 1, the air circuits may be interchanged by means of dampers (motor

driven or operated manually) to obtain either heated or cooled air for the

conditioned space. With this system one heat-exchanger coil is always the

evaporator while the other is always the condenser. The conditioned air

will pass over the evaporator coil during the cooling cycle while the

outdoor air will pass over the condenser. The change from cooling to

heating is.accomplished by positioning the dampers.

;I. water-to-air heat pump uses water as a heat source and sink and

uses air to transmit heat to or from the conditioned space.

Air-to-water heat pumps are commonly used in large buildings where

zone control is necessary, and are also sometimes employed for the

production of hot or cold water in industrial applications.

150

Common Heat Pump Types

HEIM'CXMCE-AND S INK/*

OMR.WJ ID

THERMALCYCLE

DIAGRAM

E=7;1 HEAT ING C=> COOL ING 1111* HEATING AND COOLING

A IR A I RREFR I GERANT

CHANGEOVER

OUTDOOR4. -

INDOOR

IMOMIMIOREM

Intl'

.T.

IINW 44,

friaramon'sMIMI

Z:3

S0 03

C5-4)air, COMP.

LIQUIDRECEIVER

.

A I R A r RA IR

CHANGEOVER

INDOOR )L OE 01 ciL

'''..._

GOND.......

. .

1

1OUTDOOR

1 1----a"r ,f

i----40.i=3..i

.c.........7_0

LEVAP.

WATER A 1 R

REFRIGERANTCHANGEOVER

I-CHILLER-CONDENSER :+

1111

IIIIIIIMOM

C

ti-

IIINIMMINNIIII111111111.111

IN NMI

COMP

0A I R WATER

LX.

L IQ. REC.

EARTH A I RREFRIGERANT

HANGEOVER

I .111

PIIN

11011111111111

iiianallin11.1.1.111.11

eie c oup.S5727/ r4W71AW** C4Ci eg

EMU___NI4-*,....

..,LIQUID

RECEIVER

WATER WATER

INATER it RETURNa

SOURCE 6"

WATER 1 1 CONOCHILLER e INDOOR

.HANGEOVER. COMP

-444 SUPPLY

4

* AI

D ISCHARGE

ALL SINGLE STAGE. COMPRESSION

TABLE 1

151

ASHRAE Guide & Data Book 1961

Earth-to-air heat pumps may employ direct expansion of the refrigerant

11

in an embedded coil as illustrated in Table 1, or they may be of the

indirect type described under the water-to-air type.

A water-to-water heat pump uses water as the heat source and sink for

both heating and cooling operations. Heating-cooling changeover may be

accomplished in the refrigerant circuit, but in many cases, it is more

convenient to perform the switching in the water circuits such as is

illustrated in Table 1.

In earth-toltwater heat pump (not shown in Table 1) may be like the

earth-to-air type shown except for the substitution of a refrigerant-water

heat exchanger for the finned coil shown on the indoor side. It may also

take a form similar to the water-to-water system shown when a secondary-fluid

ground coil is used.

-Some heat pumps which use the earth as the heat source and sink are essent-

ially of the water-to-air type. An antifreeze solution is pumped through a

loop comprised of a pipe coil embedded in the earth an4 the chiller-condenser.

Other types of heat pumps in addition to those listed in Table I are

possible. An example is one which utilizes solar energy as a source of heat;

its refrigerant circuit may resemble the water-to-air, air-to-air, or other

types depending upon the form of solar collector and the means of heating

and cooling distribution which is employed.

Another variation is the use of more than one heat source. Some heat

pumps have utilized air as the primary heat source, but are changed over to

extract heat from water (e.g. from a well or storage tank) during periods of

peak load. The use of solar energy requires another heat source during

periods of insufficient solar radiation.

152